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## java.lang
Class String

    java.lang.Object
      |
      +--java.lang.String

All Implemented Interfaces:
  Comparable, Serializable

public final class String
extends Object
implements Serializable, Comparable

The `String` class represents character strings. All string literals in Java programs, such as `"abc"`, are implemented as instances of this class.

Strings are constant; their values cannot be changed after they are created. String buffers support mutable strings. Because String objects are immutable they can be shared. For example:

>          String str = "abc";

is equivalent to:

>          char data[] = {'a', 'b', 'c'};
>          String str = new String(data);

Here are some more examples of how strings can be used:

>          System.out.println("abc");
>          String cde = "cde";
>          System.out.println("abc" + cde);
>          String c = "abc".substring(2,3);
>          String d = cde.substring(1, 2);

The class `String` includes methods for examining individual characters of the sequence, for comparing strings, for searching strings, for extracting substrings, and for creating a copy of a string with all characters translated to uppercase or to lowercase.

The Java language provides special support for the string concatentation operator ( + ), and for conversion of other objects to strings. String concatenation is implemented through the `StringBuffer` class and its `append` method. String conversions are implemented through the method `toString`, defined by `Object` and inherited by all classes in Java. For additional information on string concatenation and conversion, see Gosling, Joy, and Steele, The Java Language Specification.

Since:
  JDK1.0
See Also:
  `Object.toString()`, `StringBuffer`, `StringBuffer.append(boolean)`, `StringBuffer.append(char)`, `StringBuffer.append(char[])`, `StringBuffer.append(char[], int, int)`, `StringBuffer.append(double)`, `StringBuffer.append(float)`, `StringBuffer.append(int)`, `StringBuffer.append(long)`, `StringBuffer.append(java.lang.Object)`, `StringBuffer.append(java.lang.String)`, Character encodings, Serialized Form

Field Summary
`static Comparator` | `CASE_INSENSITIVE_ORDER` Returns a Comparator that orders `String` objects as by `compareToIgnoreCase`.

Constructor Summary
`String()` Initializes a newly created `String` object so that it represents an empty character sequence.
`String(byte[] bytes)` Construct a new `String` by converting the specified array of bytes using the platform's default character encoding.
`String(byte[] bytes, int offset, int length)` Construct a new `String` by converting the specified subarray of bytes using the platform's default character encoding.
`String(byte[] bytes, int offset, int length, String enc)` Construct a new `String` by converting the specified subarray of bytes using the specified character encoding.
`String(byte[] bytes, String enc)` Construct a new `String` by converting the specified array of bytes using the specified character encoding.
`String(char[] value)` Allocates a new `String` so that it represents the sequence of characters currently contained in the character array argument.
`String(char[] value, int offset, int count)` Allocates a new `String` that contains characters from a subarray of the character array argument.
`String(String value)` Initializes a newly created `String` object so that it represents the same sequence of characters as the argument; in other words, the newly created string is a copy of the argument string.
`String(StringBuffer buffer)` Allocates a new string that contains the sequence of characters currently contained in the string buffer argument.

Method Summary
`char` | `charAt(int index)` Returns the character at the specified index.
`int` | `compareTo(Object o)` Compares this String to another Object.
`int` | `compareTo(String anotherString)` Compares two strings lexicographically.
`int` | `compareToIgnoreCase(String str)` Compares two strings lexicographically, ignoring case considerations.
`String` | `concat(String str)` Concatenates the specified string to the end of this string.
`static String` | `copyValueOf(char[] data)` Returns a String that is equivalent to the specified character array.
`static String` | `copyValueOf(char[] data, int offset, int count)` Returns a String that is equivalent to the specified character array.
`boolean` | `endsWith(String suffix)` Tests if this string ends with the specified suffix.
`boolean` | `equals(Object anObject)` Compares this string to the specified object.
`boolean` | `equalsIgnoreCase(String anotherString)` Compares this `String` to another `String`, ignoring case considerations.
`byte[]` | `getBytes()` Convert this `String` into bytes according to the platform's default character encoding, storing the result into a new byte array.
`byte[]` | `getBytes(String enc)` Convert this `String` into bytes according to the specified character encoding, storing the result into a new byte array.
`void` | `getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)` Copies characters from this string into the destination character array.
`int` | `hashCode()` Returns a hashcode for this string.
`int` | `indexOf(int ch)` Returns the index within this string of the first occurrence of the specified character.
`int` | `indexOf(int ch, int fromIndex)` Returns the index within this string of the first occurrence of the specified character, starting the search at the specified index.
`int` | `indexOf(String str)` Returns the index within this string of the first occurrence of the specified substring.
`int` | `indexOf(String str, int fromIndex)` Returns the index within this string of the first occurrence of the specified substring, starting at the specified index.
`String` | `intern()` Returns a canonical representation for the string object.
`int` | `lastIndexOf(int ch)` Returns the index within this string of the last occurrence of the specified character.
`int` | `lastIndexOf(int ch, int fromIndex)` Returns the index within this string of the last occurrence of the specified character, searching backward starting at the specified index.
`int` | `lastIndexOf(String str)` Returns the index within this string of the rightmost occurrence of the specified substring.
`int` | `lastIndexOf(String str, int fromIndex)` Returns the index within this string of the last occurrence of the specified substring.
`int` | `length()` Returns the length of this string.
`boolean` | `regionMatches(boolean ignoreCase, int toffset, String other, int ooffset, int len)` Tests if two string regions are equal.
`boolean` | `regionMatches(int toffset, String other, int ooffset, int len)` Tests if two string regions are equal.
`String` | `replace(char oldChar, char newChar)` Returns a new string resulting from replacing all occurrences of `oldChar` in this string with `newChar`.
`boolean` | `startsWith(String prefix)` Tests if this string starts with the specified prefix.
`boolean` | `startsWith(String prefix, int toffset)` Tests if this string starts with the specified prefix beginning a specified index.
`String` | `substring(int beginIndex)` Returns a new string that is a substring of this string.
`String` | `substring(int beginIndex, int endIndex)` Returns a new string that is a substring of this string.
`char[]` | `toCharArray()` Converts this string to a new character array.
`String` | `toLowerCase()` Converts all of the characters in this `String` to lower case using the rules of the default locale, which is returned by `Locale.getDefault`.
`String` | `toLowerCase(Locale locale)` Converts all of the characters in this `String` to lower case using the rules of the given `Locale`.
`String` | `toString()` This object (which is already a string!) is itself returned.
`String` | `toUpperCase()` Converts all of the characters in this `String` to upper case using the rules of the default locale, which is returned by `Locale.getDefault`.
`String` | `toUpperCase(Locale locale)` Converts all of the characters in this `String` to upper case using the rules of the given locale.
`String` | `trim()` Removes white space from both ends of this string.
`static String` | `valueOf(boolean b)` Returns the string representation of the `boolean` argument.
`static String` | `valueOf(char c)` Returns the string representation of the `char` argument.
`static String` | `valueOf(char[] data)` Returns the string representation of the `char` array argument.
`static String` | `valueOf(char[] data, int offset, int count)` Returns the string representation of a specific subarray of the `char` array argument.
`static String` | `valueOf(double d)` Returns the string representation of the `double` argument.
`static String` | `valueOf(float f)` Returns the string representation of the `float` argument.
`static String` | `valueOf(int i)` Returns the string representation of the `int` argument.
`static String` | `valueOf(long l)` Returns the string representation of the `long` argument.
`static String` | `valueOf(Object obj)` Returns the string representation of the `Object` argument.

Methods inherited from class java.lang.Object
`clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

Field Detail

### CASE_INSENSITIVE_ORDER

    public static final Comparator CASE_INSENSITIVE_ORDER

  Returns a Comparator that orders `String` objects as by `compareToIgnoreCase`. This comparator is serializable.

  Note that this Comparator does not take locale into account, and will result in an unsatisfactory ordering for certain locales. The java.text package provides Collators to allow locale-sensitive ordering.

  See Also:
    `java.text.Collator#compare(String, String)`
  Since:
    1.2

Constructor Detail

### String

    public String()

  Initializes a newly created `String` object so that it represents an empty character sequence.

### String

    public String(String value)

  Initializes a newly created `String` object so that it represents the same sequence of characters as the argument; in other words, the newly created string is a copy of the argument string.
  Parameters:
    `value` - a `String`.

### String

    public String(char[] value)

  Allocates a new `String` so that it represents the sequence of characters currently contained in the character array argument. The contents of the character array are copied; subsequent modification of the character array does not affect the newly created string.
  Parameters:
    `value` - the initial value of the string.
  Throws:
    `NullPointerException` - if `value` is `null`.

### String

    public String(char[] value,
                  int offset,
                  int count)

  Allocates a new `String` that contains characters from a subarray of the character array argument. The `offset` argument is the index of the first character of the subarray and the `count` argument specifies the length of the subarray. The contents of the subarray are copied; subsequent modification of the character array does not affect the newly created string.
  Parameters:
    `value` - array that is the source of characters.
    `offset` - the initial offset.
    `count` - the length.
  Throws:
    `IndexOutOfBoundsException` - if the `offset` and `count` arguments index characters outside the bounds of the `value` array.
    `NullPointerException` - if `value` is `null`.

### String

    public String(byte[] bytes,
                  int offset,
                  int length,
                  String enc)
           throws UnsupportedEncodingException

  Construct a new `String` by converting the specified subarray of bytes using the specified character encoding. The length of the new `String` is a function of the encoding, and hence may not be equal to the length of the subarray.
  Parameters:
    `bytes` - The bytes to be converted into characters
    `offset` - Index of the first byte to convert
    `length` - Number of bytes to convert
    `enc` - The name of a supported character encoding
  Throws:
    `UnsupportedEncodingException` - if the named encoding is not supported
    `IndexOutOfBoundsException` - if the `offset` and `count` arguments index characters outside the bounds of the `value` array.
  Since:
    JDK1.1

### String

    public String(byte[] bytes,
                  String enc)
           throws UnsupportedEncodingException

  Construct a new `String` by converting the specified array of bytes using the specified character encoding. The length of the new `String` is a function of the encoding, and hence may not be equal to the length of the byte array.
  Parameters:
    `bytes` - The bytes to be converted into characters
    `enc` - The name of a supported character encoding
  Throws:
    `UnsupportedEncodingException` - If the named encoding is not supported
  Since:
    JDK1.1

### String

    public String(byte[] bytes,
                  int offset,
                  int length)

  Construct a new `String` by converting the specified subarray of bytes using the platform's default character encoding. The length of the new `String` is a function of the encoding, and hence may not be equal to the length of the subarray.
  Parameters:
    `bytes` - The bytes to be converted into characters
    `offset` - Index of the first byte to convert
    `length` - Number of bytes to convert
  Since:
    JDK1.1

### String

    public String(byte[] bytes)

  Construct a new `String` by converting the specified array of bytes using the platform's default character encoding. The length of the new `String` is a function of the encoding, and hence may not be equal to the length of the byte array.
  Parameters:
    `bytes` - The bytes to be converted into characters
  Since:
    JDK1.1

### String

    public String(StringBuffer buffer)

  Allocates a new string that contains the sequence of characters currently contained in the string buffer argument. The contents of the string buffer are copied; subsequent modification of the string buffer does not affect the newly created string.
  Parameters:
    `buffer` - a `StringBuffer`.
  Throws:
    `NullPointerException` - If `buffer` is `null`.

Method Detail

### length

    public int length()

  Returns the length of this string. The length is equal to the number of 16-bit Unicode characters in the string.
  Returns:
    the length of the sequence of characters represented by this object.

### charAt

    public char charAt(int index)

  Returns the character at the specified index. An index ranges from `0` to `length() - 1`. The first character of the sequence is at index `0`, the next at index `1`, and so on, as for array indexing.
  Parameters:
    `index` - the index of the character.
  Returns:
    the character at the specified index of this string. The first character is at index `0`.
  Throws:
    `IndexOutOfBoundsException` - if the `index` argument is negative or not less than the length of this string.

### getChars

    public void getChars(int srcBegin,
                         int srcEnd,
                         char[] dst,
                         int dstBegin)

  Copies characters from this string into the destination character array.

  The first character to be copied is at index `srcBegin`; the last character to be copied is at index `srcEnd-1` (thus the total number of characters to be copied is `srcEnd-srcBegin`). The characters are copied into the subarray of `dst` starting at index `dstBegin` and ending at index:

  >          dstbegin + (srcEnd-srcBegin) - 1

  Parameters:
    `srcBegin` - index of the first character in the string to copy.
    `srcEnd` - index after the last character in the string to copy.
    `dst` - the destination array.
    `dstBegin` - the start offset in the destination array.
  Throws:
    `IndexOutOfBoundsException` - If any of the following is true:
    - `srcBegin` is negative.
    - `srcBegin` is greater than `srcEnd`
    - `srcEnd` is greater than the length of this string
    - `dstBegin` is negative
    - `dstBegin+(srcEnd-srcBegin)` is larger than `dst.length`
    `NullPointerException` - if `dst` is `null`

### getBytes

    public byte[] getBytes(String enc)
                    throws UnsupportedEncodingException

  Convert this `String` into bytes according to the specified character encoding, storing the result into a new byte array.
  Parameters:
    `enc` - The name of a supported character encoding
  Returns:
    The resultant byte array
  Throws:
    `UnsupportedEncodingException` - If the named encoding is not supported
  Since:
    JDK1.1

### getBytes

    public byte[] getBytes()

  Convert this `String` into bytes according to the platform's default character encoding, storing the result into a new byte array.
  Returns:
    the resultant byte array.
  Since:
    JDK1.1

### equals

    public boolean equals(Object anObject)

  Compares this string to the specified object. The result is `true` if and only if the argument is not `null` and is a `String` object that represents the same sequence of characters as this object.
  Overrides:
    `equals` in class `Object`
  Parameters:
    `anObject` - the object to compare this `String` against.
  Returns:
    `true` if the `String` are equal; `false` otherwise.
  See Also:
    `compareTo(java.lang.String)`, `equalsIgnoreCase(java.lang.String)`

### equalsIgnoreCase

    public boolean equalsIgnoreCase(String anotherString)

  Compares this `String` to another `String`, ignoring case considerations. Two strings are considered equal ignoring case if they are of the same length, and corresponding characters in the two strings are equal ignoring case.

  Two characters `c1` and `c2` are considered the same, ignoring case if at least one of the following is true:

  - The two characters are the same (as compared by the `==` operator).
  - Applying the method `Character.toUpperCase(char)` to each character produces the same result.
  - Applying the method `Character.toLowerCase(char)` to each character produces the same result.
  Parameters:
    `anotherString` - the `String` to compare this `String` against.
  Returns:
    `true` if the argument is not `null` and the `String`s are equal, ignoring case; `false` otherwise.
  See Also:
    `equals(Object)`, `Character.toLowerCase(char)`, `Character.toUpperCase(char)`

### compareTo

    public int compareTo(String anotherString)

  Compares two strings lexicographically. The comparison is based on the Unicode value of each character in the strings. The character sequence represented by this `String` object is compared lexicographically to the character sequence represented by the argument string. The result is a negative integer if this `String` object lexicographically precedes the argument string. The result is a positive integer if this `String` object lexicographically follows the argument string. The result is zero if the strings are equal; `compareTo` returns `0` exactly when the `equals(Object)` method would return `true`.

  This is the definition of lexicographic ordering. If two strings are different, then either they have different characters at some index that is a valid index for both strings, or their lengths are different, or both. If they have different characters at one or more index positions, let k be the smallest such index; then the string whose character at position k has the smaller value, as determined by using the < operator, lexicographically precedes the other string. In this case, `compareTo` returns the difference of the two character values at position `k` in the two string -- that is, the value:

  >      this.charAt(k)-anotherString.charAt(k)

  If there is no index position at which they differ, then the shorter string lexicographically precedes the longer string. In this case, `compareTo` returns the difference of the lengths of the strings -- that is, the value:

  >      this.length()-anotherString.length()

  Parameters:
    `anotherString` - the `String` to be compared.
  Returns:
    the value `0` if the argument string is equal to this string; a value less than `0` if this string is lexicographically less than the string argument; and a value greater than `0` if this string is lexicographically greater than the string argument.
  Throws:
    `NullPointerException` - if `anotherString` is `null`.

### compareTo

    public int compareTo(Object o)

  Compares this String to another Object. If the Object is a String, this function behaves like `compareTo(String)`. Otherwise, it throws a `ClassCastException` (as Strings are comparable only to other Strings).
  Specified by:
    `compareTo` in interface `Comparable`
  Parameters:
    `o` - the `Object` to be compared.
  Returns:
    the value `0` if the argument is a string lexicographically equal to this string; a value less than `0` if the argument is a string lexicographically greater than this string; and a value greater than `0` if the argument is a string lexicographically less than this string.
  Throws:
    ``ClassCastException`` - if the argument is not a `String`.
  Since:
    1.2
  See Also:
    `Comparable`

### compareToIgnoreCase

    public int compareToIgnoreCase(String str)

  Compares two strings lexicographically, ignoring case considerations. This method returns an integer whose sign is that of `this.toUpperCase().toLowerCase().compareTo( str.toUpperCase().toLowerCase())`.

  Note that this method does not take locale into account, and will result in an unsatisfactory ordering for certain locales. The java.text package provides collators to allow locale-sensitive ordering.

  Parameters:
    `str` - the `String` to be compared.
  Returns:
    a negative integer, zero, or a positive integer as the the specified String is greater than, equal to, or less than this String, ignoring case considerations.
  Since:
    1.2
  See Also:
    `java.text.Collator#compare(String, String)`

### regionMatches

    public boolean regionMatches(int toffset,
                                 String other,
                                 int ooffset,
                                 int len)

  Tests if two string regions are equal.

  A substring of this `String` object is compared to a substring of the argument other. The result is true if these substrings represent identical character sequences. The substring of this `String` object to be compared begins at index `toffset` and has length `len`. The substring of other to be compared begins at index `ooffset` and has length `len`. The result is `false` if and only if at least one of the following is true:

  - `toffset` is negative.
  - `ooffset` is negative.
  - `toffset+len` is greater than the length of this `String` object.
  - `ooffset+len` is greater than the length of the other argument.
  - There is some nonnegative integer k less than `len` such that: `this.charAt(toffset+k) != other.charAt(ooffset+k)`
  Parameters:
    `toffset` - the starting offset of the subregion in this string.
    `other` - the string argument.
    `ooffset` - the starting offset of the subregion in the string argument.
    `len` - the number of characters to compare.
  Returns:
    `true` if the specified subregion of this string exactly matches the specified subregion of the string argument; `false` otherwise.
  Throws:
    `NullPointerException` - if `other` is `null`.

### regionMatches

    public boolean regionMatches(boolean ignoreCase,
                                 int toffset,
                                 String other,
                                 int ooffset,
                                 int len)

  Tests if two string regions are equal.

  A substring of this `String` object is compared to a substring of the argument `other`. The result is `true` if these substrings represent character sequences that are the same, ignoring case if and only if `ignoreCase` is true. The substring of this `String` object to be compared begins at index `toffset` and has length `len`. The substring of `other` to be compared begins at index `ooffset` and has length `len`. The result is `false` if and only if at least one of the following is true:

  - `toffset` is negative.
  - `ooffset` is negative.
  - `toffset+len` is greater than the length of this `String` object.
  - `ooffset+len` is greater than the length of the other argument.
  - There is some nonnegative integer k less than `len` such that:

    >      this.charAt(toffset+k) != other.charAt(ooffset+k)

  - `ignoreCase` is `true` and there is some nonnegative integer k less than `len` such that:

    >      Character.toLowerCase(this.charAt(toffset+k)) !=
    >     Character.toLowerCase(other.charAt(ooffset+k))

    and:

    >      Character.toUpperCase(this.charAt(toffset+k)) !=
    >              Character.toUpperCase(other.charAt(ooffset+k))

  Parameters:
    `ignoreCase` - if `true`, ignore case when comparing characters.
    `toffset` - the starting offset of the subregion in this string.
    `other` - the string argument.
    `ooffset` - the starting offset of the subregion in the string argument.
    `len` - the number of characters to compare.
  Returns:
    `true` if the specified subregion of this string matches the specified subregion of the string argument; `false` otherwise. Whether the matching is exact or case insensitive depends on the `ignoreCase` argument.

### startsWith

    public boolean startsWith(String prefix,
                              int toffset)

  Tests if this string starts with the specified prefix beginning a specified index.
  Parameters:
    `prefix` - the prefix.
    `toffset` - where to begin looking in the string.
  Returns:
    `true` if the character sequence represented by the argument is a prefix of the substring of this object starting at index `toffset`; `false` otherwise. The result is `false` if `toffset` is negative or greater than the length of this `String` object; otherwise the result is the same as the result of the expression

                  this.subString(toffset).startsWith(prefix)

  Throws:
    `NullPointerException` - if `prefix` is `null`.

### startsWith

    public boolean startsWith(String prefix)

  Tests if this string starts with the specified prefix.
  Parameters:
    `prefix` - the prefix.
  Returns:
    `true` if the character sequence represented by the argument is a prefix of the character sequence represented by this string; `false` otherwise. Note also that `true` will be returned if the argument is an empty string or is equal to this `String` object as determined by the `equals(Object)` method.
  Throws:
    `NullPointerException` - if `prefix` is `null`.
  Since:
    JDK1. 0

### endsWith

    public boolean endsWith(String suffix)

  Tests if this string ends with the specified suffix.
  Parameters:
    `suffix` - the suffix.
  Returns:
    `true` if the character sequence represented by the argument is a suffix of the character sequence represented by this object; `false` otherwise. Note that the result will be `true` if the argument is the empty string or is equal to this `String` object as determined by the `equals(Object)` method.
  Throws:
    `NullPointerException` - if `suffix` is `null`.

### hashCode

    public int hashCode()

  Returns a hashcode for this string. The hashcode for a `String` object is computed as

  >      s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]

  using `int` arithmetic, where `s[i]` is the ith character of the string, `n` is the length of the string, and `^` indicates exponentiation. (The hash value of the empty string is zero.)
  Overrides:
    `hashCode` in class `Object`
  Returns:
    a hash code value for this object.

### indexOf

    public int indexOf(int ch)

  Returns the index within this string of the first occurrence of the specified character. If a character with value `ch` occurs in the character sequence represented by this `String` object, then the index of the first such occurrence is returned -- that is, the smallest value k such that:

  >      this.charAt(k) == ch

  is `true`. If no such character occurs in this string, then `-1` is returned.
  Parameters:
    `ch` - a character.
  Returns:
    the index of the first occurrence of the character in the character sequence represented by this object, or `-1` if the character does not occur.

### indexOf

    public int indexOf(int ch,
                       int fromIndex)

  Returns the index within this string of the first occurrence of the specified character, starting the search at the specified index.

  If a character with value `ch` occurs in the character sequence represented by this `String` object at an index no smaller than `fromIndex`, then the index of the first such occurrence is returned--that is, the smallest value k such that:

  >      (this.charAt(k) == ch) && (k >= fromIndex)

  is true. If no such character occurs in this string at or after position `fromIndex`, then `-1` is returned.

  There is no restriction on the value of `fromIndex`. If it is negative, it has the same effect as if it were zero: this entire string may be searched. If it is greater than the length of this string, it has the same effect as if it were equal to the length of this string: `-1` is returned.

  Parameters:
    `ch` - a character.
    `fromIndex` - the index to start the search from.
  Returns:
    the index of the first occurrence of the character in the character sequence represented by this object that is greater than or equal to `fromIndex`, or `-1` if the character does not occur.

### lastIndexOf

    public int lastIndexOf(int ch)

  Returns the index within this string of the last occurrence of the specified character. That is, the index returned is the largest value k such that:

  >      this.charAt(k) == ch

  is true. The String is searched backwards starting at the last character.
  Parameters:
    `ch` - a character.
  Returns:
    the index of the last occurrence of the character in the character sequence represented by this object, or `-1` if the character does not occur.

### lastIndexOf

    public int lastIndexOf(int ch,
                           int fromIndex)

  Returns the index within this string of the last occurrence of the specified character, searching backward starting at the specified index. That is, the index returned is the largest value k such that:

  >      this.charAt(k) == ch) && (k <= fromIndex)

  is true.
  Parameters:
    `ch` - a character.
    `fromIndex` - the index to start the search from. There is no restriction on the value of `fromIndex`. If it is greater than or equal to the length of this string, it has the same effect as if it were equal to one less than the length of this string: this entire string may be searched. If it is negative, it has the same effect as if it were -1: -1 is returned.
  Returns:
    the index of the last occurrence of the character in the character sequence represented by this object that is less than or equal to `fromIndex`, or `-1` if the character does not occur before that point.

### indexOf

    public int indexOf(String str)

  Returns the index within this string of the first occurrence of the specified substring. The integer returned is the smallest value k such that:

  >      this.startsWith(str, k)

  is `true`.
  Parameters:
    `str` - any string.
  Returns:
    if the string argument occurs as a substring within this object, then the index of the first character of the first such substring is returned; if it does not occur as a substring, `-1` is returned.
  Throws:
    `NullPointerException` - if `str` is `null`.

### indexOf

    public int indexOf(String str,
                       int fromIndex)

  Returns the index within this string of the first occurrence of the specified substring, starting at the specified index. The integer returned is the smallest value k such that:

  >      this.startsWith(str, k) && (k >= fromIndex)

  is `true`.

  There is no restriction on the value of `fromIndex`. If it is negative, it has the same effect as if it were zero: this entire string may be searched. If it is greater than the length of this string, it has the same effect as if it were equal to the length of this string: `-1` is returned.

  Parameters:
    `str` - the substring to search for.
    `fromIndex` - the index to start the search from.
  Returns:
    If the string argument occurs as a substring within this object at a starting index no smaller than `fromIndex`, then the index of the first character of the first such substring is returned. If it does not occur as a substring starting at `fromIndex` or beyond, `-1` is returned.
  Throws:
    `NullPointerException` - if `str` is `null`

### lastIndexOf

    public int lastIndexOf(String str)

  Returns the index within this string of the rightmost occurrence of the specified substring. The rightmost empty string "" is considered to occur at the index value `this.length()`. The returned index is the largest value k such that

  >      this.startsWith(str, k)

  is true.
  Parameters:
    `str` - the substring to search for.
  Returns:
    if the string argument occurs one or more times as a substring within this object, then the index of the first character of the last such substring is returned. If it does not occur as a substring, `-1` is returned.
  Throws:
    `NullPointerException` - if `str` is `null`.

### lastIndexOf

    public int lastIndexOf(String str,
                           int fromIndex)

  Returns the index within this string of the last occurrence of the specified substring. The returned index indicates the start of the substring, and it must be equal to or less than `fromIndex`. That is, the index returned is the largest value k such that:

  >      this.startsWith(str, k) && (k <= fromIndex)

  Parameters:
    `str` - the substring to search for.
    `fromIndex` - the index to start the search from. There is no restriction on the value of fromIndex. If it is greater than the length of this string, it has the same effect as if it were equal to the length of this string: this entire string may be searched. If it is negative, it has the same effect as if it were -1: -1 is returned.
  Returns:
    If the string argument occurs one or more times as a substring within this object at a starting index no greater than `fromIndex`, then the index of the first character of the last such substring is returned. If it does not occur as a substring starting at `fromIndex` or earlier, `-1` is returned.
  Throws:
    `NullPointerException` - if `str` is `null`.

### substring

    public String substring(int beginIndex)

  Returns a new string that is a substring of this string. The substring begins with the character at the specified index and extends to the end of this string.

  Examples:

  >      "unhappy".substring(2) returns "happy"
  >      "Harbison".substring(3) returns "bison"
  >      "emptiness".substring(9) returns "" (an empty string)

  Parameters:
    `beginIndex` - the beginning index, inclusive.
  Returns:
    the specified substring.
  Throws:
    `IndexOutOfBoundsException` - if `beginIndex` is negative or larger than the length of this `String` object.

### substring

    public String substring(int beginIndex,
                            int endIndex)

  Returns a new string that is a substring of this string. The substring begins at the specified `beginIndex` and extends to the character at index `endIndex - 1`. Thus the length of the substring is `endIndex-beginIndex`.

  Examples:

  >      "hamburger".substring(4, 8) returns "urge"
  >      "smiles".substring(1, 5) returns "mile"

  Parameters:
    `beginIndex` - the beginning index, inclusive.
    `endIndex` - the ending index, exclusive.
  Returns:
    the specified substring.
  Throws:
    `IndexOutOfBoundsException` - if the `beginIndex` is negative, or `endIndex` is larger than the length of this `String` object, or `beginIndex` is larger than `endIndex`.

### concat

    public String concat(String str)

  Concatenates the specified string to the end of this string.

  If the length of the argument string is `0`, then this `String` object is returned. Otherwise, a new `String` object is created, representing a character sequence that is the concatenation of the character sequence represented by this `String` object and the character sequence represented by the argument string.

  Examples:

  >      "cares".concat("s") returns "caress"
  >      "to".concat("get").concat("her") returns "together"

  Parameters:
    `str` - the `String` that is concatenated to the end of this `String`.
  Returns:
    a string that represents the concatenation of this object's characters followed by the string argument's characters.
  Throws:
    `NullPointerException` - if `str` is `null`.

### replace

    public String replace(char oldChar,
                          char newChar)

  Returns a new string resulting from replacing all occurrences of `oldChar` in this string with `newChar`.

  If the character `oldChar` does not occur in the character sequence represented by this `String` object, then a reference to this `String` object is returned. Otherwise, a new `String` object is created that represents a character sequence identical to the character sequence represented by this `String` object, except that every occurrence of `oldChar` is replaced by an occurrence of `newChar`.

  Examples:

  >      "mesquite in your cellar".replace('e', 'o')
  >              returns "mosquito in your collar"
  >      "the war of baronets".replace('r', 'y')
  >              returns "the way of bayonets"
  >      "sparring with a purple porpoise".replace('p', 't')
  >              returns "starring with a turtle tortoise"
  >      "JonL".replace('q', 'x') returns "JonL" (no change)

  Parameters:
    `oldChar` - the old character.
    `newChar` - the new character.
  Returns:
    a string derived from this string by replacing every occurrence of `oldChar` with `newChar`.

### toLowerCase

    public String toLowerCase(Locale locale)

  Converts all of the characters in this `String` to lower case using the rules of the given `Locale`. Usually, the characters are converted by calling `Character.toLowerCase`. Exceptions to this rule are listed in the following table:

  Language Code of Locale | Upper Case | Lower Case | Description
  --- | --- | --- | ---
  tr (Turkish) | \u0130 | \u0069 | capital letter I with dot above -> small letter i
  tr (Turkish) | \u0049 | \u0131 | capital letter I -> small letter dotless i

  Parameters:
    `locale` - use the case transformation rules for this locale
  Returns:
    the String, converted to lowercase.
  Since:
    JDK1.1
  See Also:
    `Character.toLowerCase(char)`, `toUpperCase(Locale)`

### toLowerCase

    public String toLowerCase()

  Converts all of the characters in this `String` to lower case using the rules of the default locale, which is returned by `Locale.getDefault`.

  If no character in the string has a different lowercase version, based on calling the `toLowerCase` method defined by `Character`, then the original string is returned.

  Otherwise, this method creates a new `String` object that represents a character sequence identical in length to the character sequence represented by this String object, with every character equal to the result of applying the method `Character.toLowerCase` to the corresponding character of this `String` object.

  Examples:

  >      "French Fries".toLowerCase() returns "french fries"
  >      "".toLowerCase() returns ""

  Returns:
    the string, converted to lowercase.
  See Also:
    `Character.toLowerCase(char)`, `toLowerCase(Locale)`

### toUpperCase

    public String toUpperCase(Locale locale)

  Converts all of the characters in this `String` to upper case using the rules of the given locale. Usually, the characters are converted by calling `Character.toUpperCase`. Exceptions to this rule are listed in the following table:

  Language Code of Locale | Lower Case | Upper Case | Description
  --- | --- | --- | ---
  tr (Turkish) | \u0069 | \u0130 | small letter i -> capital letter I with dot above
  tr (Turkish) | \u0131 | \u0049 | small letter dotless i -> capital letter I
  (all) | \u00df | \u0053 \u0053 | small letter sharp s -> two letters: SS

  Parameters:
    `locale` - use the case transformation rules for this locale
  Returns:
    the String, converted to uppercase.
  Since:
    JDK1.1
  See Also:
    `Character.toUpperCase(char)`, `toLowerCase(Locale)`

### toUpperCase

    public String toUpperCase()

  Converts all of the characters in this `String` to upper case using the rules of the default locale, which is returned by `Locale.getDefault`.

  If no character in this string has a different uppercase version, based on calling the `toUpperCase` method defined by `Character`, then the original string is returned.

  Otherwise, this method creates a new `String` object representing a character sequence identical in length to the character sequence represented by this `String` object and with every character equal to the result of applying the method `Character.toUpperCase` to the corresponding character of this `String` object.

  Examples:

  >      "Fahrvergnügen".toUpperCase() returns "FAHRVERGNÜGEN"
  >      "Visit Ljubinje!".toUpperCase() returns "VISIT LJUBINJE!"

  Returns:
    the string, converted to uppercase.
  See Also:
    `Character.toUpperCase(char)`, `toUpperCase(Locale)`

### trim

    public String trim()

  Removes white space from both ends of this string.

  If this `String` object represents an empty character sequence, or the first and last characters of character sequence represented by this `String` object both have codes greater than `'\u0020'` (the space character), then a reference to this `String` object is returned.

  Otherwise, if there is no character with a code greater than `'\u0020'` in the string, then a new `String` object representing an empty string is created and returned.

  Otherwise, let k be the index of the first character in the string whose code is greater than `'\u0020'`, and let m be the index of the last character in the string whose code is greater than `'\u0020'`. A new `String` object is created, representing the substring of this string that begins with the character at index k and ends with the character at index m-that is, the result of `this.substring(k, m+1)`.

  This method may be used to trim `whitespace` from the beginning and end of a string; in fact, it trims all ASCII control characters as well.

  Returns:
    this string, with white space removed from the front and end.

### toString

    public String toString()

  This object (which is already a string!) is itself returned.
  Overrides:
    `toString` in class `Object`
  Returns:
    the string itself.

### toCharArray

    public char[] toCharArray()

  Converts this string to a new character array.
  Returns:
    a newly allocated character array whose length is the length of this string and whose contents are initialized to contain the character sequence represented by this string.

### valueOf

    public static String valueOf(Object obj)

  Returns the string representation of the `Object` argument.
  Parameters:
    `obj` - an `Object`.
  Returns:
    if the argument is `null`, then a string equal to `"null"`; otherwise, the value of `obj.toString()` is returned.
  See Also:
    `Object.toString()`

### valueOf

    public static String valueOf(char[] data)

  Returns the string representation of the `char` array argument. The contents of the character array are copied; subsequent modification of the character array does not affect the newly created string.
  Parameters:
    `data` - a `char` array.
  Returns:
    a newly allocated string representing the same sequence of characters contained in the character array argument.

### valueOf

    public static String valueOf(char[] data,
                                 int offset,
                                 int count)

  Returns the string representation of a specific subarray of the `char` array argument.

  The `offset` argument is the index of the first character of the subarray. The `count` argument specifies the length of the subarray. The contents of the subarray are copied; subsequent modification of the character array does not affect the newly created string.

  Parameters:
    `data` - the character array.
    `offset` - the initial offset into the value of the `String`.
    `count` - the length of the value of the `String`.
  Returns:
    a newly allocated string representing the sequence of characters contained in the subarray of the character array argument.
  Throws:
    `NullPointerException` - if `data` is `null`.
    `IndexOutOfBoundsException` - if `offset` is negative, or `count` is negative, or `offset+count` is larger than `data.length`.

### copyValueOf

    public static String copyValueOf(char[] data,
                                     int offset,
                                     int count)

  Returns a String that is equivalent to the specified character array. It creates a new array and copies the characters into it.
  Parameters:
    `data` - the character array.
    `offset` - initial offset of the subarray.
    `count` - length of the subarray.
  Returns:
    a `String` that contains the characters of the specified subarray of the character array.

### copyValueOf

    public static String copyValueOf(char[] data)

  Returns a String that is equivalent to the specified character array. It creates a new array and copies the characters into it.
  Parameters:
    `data` - the character array.
  Returns:
    a `String` that contains the characters of the character array.

### valueOf

    public static String valueOf(boolean b)

  Returns the string representation of the `boolean` argument.
  Parameters:
    `b` - a `boolean`.
  Returns:
    if the argument is `true`, a string equal to `"true"` is returned; otherwise, a string equal to `"false"` is returned.

### valueOf

    public static String valueOf(char c)

  Returns the string representation of the `char` argument.
  Parameters:
    `c` - a `char`.
  Returns:
    a newly allocated string of length `1` containing as its single character the argument `c`.

### valueOf

    public static String valueOf(int i)

  Returns the string representation of the `int` argument.

  The representation is exactly the one returned by the `Integer.toString` method of one argument.

  Parameters:
    `i` - an `int`.
  Returns:
    a newly allocated string containing a string representation of the `int` argument.
  See Also:
    `Integer.toString(int, int)`

### valueOf

    public static String valueOf(long l)

  Returns the string representation of the `long` argument.

  The representation is exactly the one returned by the `Long.toString` method of one argument.

  Parameters:
    `l` - a `long`.
  Returns:
    a newly allocated string containing a string representation of the `long` argument.
  See Also:
    `Long.toString(long)`

### valueOf

    public static String valueOf(float f)

  Returns the string representation of the `float` argument.

  The representation is exactly the one returned by the `Float.toString` method of one argument.

  Parameters:
    `f` - a `float`.
  Returns:
    a newly allocated string containing a string representation of the `float` argument.
  See Also:
    `Float.toString(float)`

### valueOf

    public static String valueOf(double d)

  Returns the string representation of the `double` argument.

  The representation is exactly the one returned by the `Double.toString` method of one argument.

  Parameters:
    `d` - a `double`.
  Returns:
    a newly allocated string containing a string representation of the `double` argument.
  See Also:
    `Double.toString(double)`

### intern

    public String intern()

  Returns a canonical representation for the string object.

  A pool of strings, initially empty, is maintained privately by the class `String`.

  When the intern method is invoked, if the pool already contains a string equal to this `String` object as determined by the `equals(Object)` method, then the string from the pool is returned. Otherwise, this `String` object is added to the pool and a reference to this `String` object is returned.

  It follows that for any two strings `s` and `t`, `s.intern() == t.intern()` is `true` if and only if `s.equals(t)` is `true`.

  All literal strings and string-valued constant expressions are interned. String literals are defined in §3.10.5 of the Java Language Specification

  Returns:
    a string that has the same contents as this string, but is guaranteed to be from a pool of unique strings.

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