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Chapter 12 The java.lang Package |
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Chapter 12 The java.lang Package |
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java.lang.String
java.lang.Object
None
java.io.Serializable
JDK 1.0 or later
The String class represents sequences of characters. Once a String object is created, it is immutable. In other words, the sequence of characters that a String represents cannot be changed after it is created. The StringBuffer class, on the other hand, represents a sequence of characters that can be changed. StringBuffer objects are used to perform computations on String objects.
The String class includes a number of utility methods, such as methods for fetching individual characters or ranges of contiguous characters, for translating characters to upper- or lowercase, for searching strings, and for parsing numeric values in strings.
String literals are compiled into String objects. Where a String literal appears in an expression, the compiled code contains a String object. If s is declared as String, the following two expressions are identical:
s.equals("ABC")
"ABC".equals(s)
The string concatenation operator implicitly creates String objects.
public final class java.lang.String extends java.lang.Object {
// Constructors
public String();
public String(byte[] bytes); // New in 1.1
public String(byte[] bytes, String enc); // New in 1.1
public String(byte[] bytes, int offset, int length); // New in 1.1
public String(byte[] bytes, int offset,
int length, String enc); // New in 1.1
public String(byte[] lowbytes, int hibyte); // Deprecated in 1.1
public String(byte[] lowbytes, int hibyte,
int offset, int count); // Deprecated in 1.1
public String(char[] value);
public String(char[] value, int offset, int;
public String(String value);
public String(StringBuffer buffer);
// Class Methods
public static String copyValueOf(char data[]);
public static String copyValueOf(char data[], int offset, int count);
public static String valueOf(boolean b);
public static String valueOf(char c);
public static String valueOf(char[] data);
public static String valueOf(char[] data, int offset, int count);
public static String valueOf(double d);
public static String valueOf(float f);
public static String valueOf(int i);
public static String valueOf(long l);
public static String valueOf(Object obj);
// Instance Methods
public char charAt(int index);
public int compareTo(String anotherString);
public String concat(String str);
public boolean endsWith(String suffix);
public boolean equals(Object anObject);
public boolean equalsIgnoreCase(String anotherString);
public byte[] getBytes(); // New in 1.1
public byte[] getBytes(String enc); // New in 1.1
public void getBytes(int srcBegin, int srcEnd,
byte[] dst, int dstBegin); // Deprecated in 1.1
public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin);
public int hashCode();
public int indexOf(int ch);
public int indexOf(int ch, int fromIndex);
public int indexOf(String str);
public int indexOf(String str, int fromIndex);
public native String intern();
public int lastIndexOf(int ch);
public int lastIndexOf(int ch, int fromIndex);
public int lastIndexOf(String str);
public int lastIndexOf(String str, int fromIndex;
public int length();
public boolean regionMatches(boolean ignoreCase, int toffset,
String other, int ooffset, int len);
public boolean regionMatches(int toffset, String other,
int ooffset, int len);
public String replace(char oldChar, char newChar);
public boolean startsWith(String prefix);
public boolean startsWith(String prefix, int toffset);
public String substring(int beginIndex);
public String substring(int beginIndex, int endIndex);
public char[] toCharArray();
public String toLowerCase();
public String toLowerCase(Locale locale); // New in 1.1
public String toString();
public String toUpperCase();
public String toUpperCase(Locale locale); // New in 1.1
public String trim();
}
New as of JDK 1.1
An array of byte values.
Creates a new String object that represents the sequence of characters stored in the given bytes array. The bytes in the array are converted to characters using the system's default character encoding scheme.
New as of JDK 1.1
An array of byte values.
The name of an encoding scheme.
If enc is not a supported encoding scheme.
Creates a new String object that represents the sequence of characters stored in the given bytes array. The bytes in the array are converted to characters using the specified character encoding scheme.
New as of JDK 1.1
An array of byte values.
An offset into the array.
The number of bytes to be included.
If offset or length indexes an element that is outside the bounds of the bytes array.
Creates a new String object that represents the sequence of characters stored in the specified portion of the given bytes array. The bytes in the array are converted to characters using the system's default character encoding scheme.
public String(byte[] bytes, int offset, int length, String enc)
New as of JDK 1.1
An array of byte values.
An offset into the array.
The number of bytes to be included.
The name of an encoding scheme.
If offset or length indexes an element that is outside the bounds of the bytes array.
If enc is not a supported encoding scheme.
Creates a new String object that represents the sequence of characters stored in the specified portion of the given bytes array. The bytes in the array are converted to characters using the specified character encoding scheme.
Deprecated as of JDK 1.1
An array of byte values.
The value to be put in the high-order byte of each 16-bit character.
Creates a new String object that represents the sequence of characters stored in the given lowbytes array. The type of the array elements is byte, which is an 8-bit data type, so each element must be converted to a char, which is a 16-bit data type. The value of the hibyte argument is used to provide the value of the high-order byte when the byte values in the array are converted to char values.
More specifically, for each element i in the array lowbytes, the character at position i in the created String object is:
((hibyte & 0xff)<<8) | lowbytes[i]
This method is deprecated as of JDK 1.1 because it does not convert bytes into characters properly. You should instead use one of the constructors that takes a specific character encoding argument or that uses the default encoding.
public String(byte[] lowbytes, int hibyte, int offset, int count)
Deprecated as of JDK 1.1
An array of byte values.
The value to be put in the high-order byte of each 16-bit character.
An offset into the array.
The number of bytes from the array to be included in the string.
If offset or count indexes an element that is outside the bounds of the lowbytes array.
Creates a new String object that represents the sequence of characters stored in the specified portion of the lowbytes array. That is, the portion of the array that starts at offset elements from the beginning of the array and is count elements long.
The type of the array elements is byte, which is an 8-bit data type, so each element must be converted to a char, which is a 16-bit data type. The value of the hibyte argument is used to provide the value of the high-order byte when the byte values in the array are converted to char values.
More specifically, for each element i in the array lowbytes that is included in the String object, the character at position i in the created String is:
((hibyte & 0xff)<<8) | lowbytes[I]
This method is deprecated as of JDK 1.1 because it does not convert bytes into characters properly. You should instead use one of the constructors that takes a specific character encoding argument or that uses the default encoding.
An array of char values.
Creates a new String object that represents the sequence of characters stored in the given array.
An array of char values.
An offset into the array.
The number of characters from the array to be included in the string.
If offset or count indexes an element that is outside the bounds of the value array.
Creates a new String object that represents the sequence of characters stored in the specified portion of the given array. That is, the portion of the given array that starts at offset elements from the beginning of the array and is count elements long.
A String object.
Creates a new String object that represents the same sequence of characters as the given String object.
A StringBuffer object.
Creates a new String object that represents the same sequence of characters as the given object.
An array of char values.
A new String object that represents the sequence of characters stored in the given array.
This method returns a new String object that represents the character sequence contained in the given array. The String object produced by this method is guaranteed not to refer to the given array, but instead to use a copy. Because the String object uses a copy of the array, subsequent changes to the array do not change the contents of this String object.
This method is now obsolete. The same result can be obtained using the valueOf() method that takes an array of char values.
public static String copyValueOf(char data[], int offset, int count)
An array of char values.
An offset into the array.
The number of characters from the array to be included in the string.
A new String object that represents the sequence of characters stored in the specified portion of the given array.
If offset or count indexes an element that is outside the bounds of the data array.
This method returns a new String object that represents the character sequence contained in the specified portion of the given array. That is, the portion of the given array that starts at offset elements from the beginning of the array and is count elements long. The String object produced by this method is guaranteed not to refer to the given array, but instead to use a copy. Because the String object uses a copy of the array, subsequent changes to the array do not change the contents of this String object.
This method is obsolete. The same result can be obtained by using the valueOf() method that takes an array of char values, an offset, and a count.
A char value.
A new String object that contains just the given character.
This method returns a string representation of a char value. In other words, it returns a String object that contains just the given character.
An array of char values.
A new String object that contains the sequence of characters stored in the given array.
This method returns a string representation of an array of char values. In other words, it returns a String object that contains the sequence of characters stored in the given array.
public static String valueOf(char[] data, int offset, int count)
An array of char values.
An offset into the array.
The number of characters from the array to be included in the string.
A new String object that contains the sequence of characters stored in the specified portion of the given array.
If offset or count indexes an element that is outside the bounds of the data array.
This method returns a string representation of the specified portion of an array of char values. In other words, it returns a String object that contains the sequence of characters in the given array that starts offset elements from the beginning of the array and is count elements long.
A double value.
A new String object that contains a string representation of the given double value.
This method returns a string representation of a double value. In other words, it returns the String object returned by Double.toString(d).
A float value.
A new String object that contains a string representation of the given float value.
This method returns a string representation of a float value. In other words, it returns the String object returned by Float.toString(f).
An int value.
A new String object that contains a string representation of the given int value.
This method returns a string representation of an int value. In other words, it returns the String object returned by Integer.toString(i).
A long value.
A new String object that contains a string representation of the given long value.
This method returns a string representation of a long value. In other words, it returns the String object returned by Long.toString(l).
A reference to an object.
A new String that contains a string representation of the given object.
This method returns a string representation of the given object. If obj is null, the method returns'null'. Otherwise, the method returns the String object returned by the toString() method of the object.
An index into the string.
The character at the specified position in this string.
If index is less than zero or greater than or equal to the length of the string.
This method returns the character at the specified position in the String object; the first character in the string is at position 0.
The String object to be compared.
A positive value if this string is greater than anotherString, 0 if the two strings are the same, or a negative value if this string is less than anotherString.
This method lexicographically compares this String object to anotherString.
Here is how the comparison works: the two String objects are compared character-by-character, starting at index 0 and continuing until a position is found in which the two strings contain different characters or until all of the characters in the shorter string have been compared. If the characters at k are different, the method returns:
this.charAt(k)-anotherString.charAt(k)
Otherwise, the comparison is based on the lengths of the strings and the method returns:
this.length()-anotherString.length()
The String object to be concatenated.
A new String object that contains the character sequences of this string and str concatenated together.
This method returns a new String object that concatenates the characters from the argument string str onto the characters from this String object. Although this is a good way to concatenate two strings, concatenating more than two strings can be done more efficiently using a StringBuffer object.
The String object suffix to be tested.
true if this string ends with the sequence of characters specified by suffix; otherwise false.
This method determines whether or not this String object ends with the specified suffix.
The Object to be compared.
true if the objects are equal; false if they are not.
Object.equals()
This method returns true if anObject is an instance of String and it contains the same sequence of characters as this String object.
Note the difference between this method and the == operator, which only returns true if both of its arguments are references to the same object.
The String object to be compared.
true if the strings are equal, ignoring case; otherwise false.
This method determines whether or not this String object contains the same sequence of characters, ignoring case, as anotherString. More specifically, corresponding characters in the two strings are considered equal if any of the following conditions are true:
public byte[] getBytes()
New as of JDK 1.1
A byte array that contains the characters of this String.
This method converts the characters in this String object to an array of byte values. The characters in the string are converted to bytes using the system's default character encoding scheme.
public byte[] getBytes(String enc)
New as of JDK 1.1
The name of an encoding scheme.
A byte array that contains the characters of this String.
If enc is not a supported encoding scheme.
This method converts the characters in this String object to an array of byte values. The characters in the string are converted to bytes using the specified character encoding scheme.
public void getBytes(int srcBegin, int srcEnd, byte[] dst, int dstBegin)
Deprecated as of JDK 1.1
The index of the first character to be copied.
The index after the last character to be copied.
The destination byte array.
An offset into the destination array.
If srcBegin, srcEnd, or dstBegin is out of range.
This method copies the low-order byte of each character in the specified range of this String object to the given array of byte values. More specifically, the first character to be copied is at index srcBegin; the last character to be copied is at index srcEnd-1. The low-order bytes of these characters are copied into dst, starting at index dstBegin and ending at index:
dstBegin + (srcEnd-srcBegin) - 1
This method is deprecated as of JDK 1.1 because it does not convert characters into bytes properly. You should instead use the getBytes() method that takes a specific character encoding argument or the one that uses the default encoding.
public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)
The index of the first character to be copied.
The index after the last character to be copied.
The destination char array.
An offset into the destination array.
If srcBegin, srcEnd, or dstBegin is out of range.
This method copies each character in the specified range of this String object to the given array of char values. More specifically, the first character to be copied is at index srcBegin; the last character to be copied is at index srcEnd-1. These characters are copied into dst, starting at index dstBegin and ending at index:
dstBegin + (srcEnd-srcBegin) - 1
A hashcode based on the sequence of characters in this string.
Object.hashCode()
This method returns a hashcode based on the sequence of characters this String object represents.
More specifically, one of two algorithms is used to compute a hash code for the string, depending on its length. If n is the length of the string and S_i is the character at position i in the string, then if n = 15 the method returns:
If n > 15, the method returns:
A char value.
The index of the first occurrence of the given character in this string or -1 if the character does not occur.
This method returns the index of the first occurrence of the given character in this String object. If there is no such occurrence, the method returns the value -1.
A char value.
The index where the search is to begin.
The index of the first occurrence of the given character in this string after fromIndex or -1 if the character does not occur.
This method returns the index of the first occurrence of the given character in this String object after ignoring the first fromIndex characters. If there is no such occurrence, the method returns the value -1.
A String object.
The index of the first occurrence of str in this string or -1 if the substring does not occur.
This method returns the index of the first character of the first occurrence of the substring str in this String object. If there is no such occurrence, the method returns the value -1.
A String object.
The index where the search is to begin.
The index of the first occurrence of str in this string after fromIndex or -1 if the substring does not occur.
This method returns the index of the first character of the first occurrence of the substring str in this String object after ignoring the first fromIndex characters. If there is no such occurrence, the method returns the value -1.
A String object that is guaranteed to be the same object for every String that contains the same character sequence.
This method returns a canonical representation for this String object. The returned String object is guaranteed to be the same String object for every String object that contains the same character sequence. In other words, if:
s1.equals(s2)
then:
s1.intern() == s2.intern()
The intern() method is used by the Java environment to ensure that String literals and constant-value String expressions that contain the same sequence of characters are all represented by a single String object.
A char value.
The index of the last occurrence of the given character in this string or -1 if the character does not occur.
This method returns the index of the last occurrence of the given character in this String object. If there is no such occurrence, the method returns the value -1.
A char value.
The index where the search is to begin.
The index of the last occurrence of the given character in this string after fromIndex or -1 if the character does not occur.
This method returns the index of the last occurrence of the given character in this String object after ignoring the first fromIndex characters. If there is no such occurrence, the method returns the value -1.
A String object.
The index of the last occurrence of str in this string or -1 if the substring does not occur.
This method returns the index of the first character of the last occurrence of the substring str in this String object. If there is no such occurrence, the method returns the value -1.
A String object.
The index where the search is to begin.
The index of the last occurrence of str in this string after fromIndex or -1 if the substring does not occur.
This method returns the index of the first character of the last occurrence of the substring str in this String object after ignoring the first fromIndex characters. If there is no such occurrence, the method returns the value -1.
The length of the character sequence represented by this string.
This method returns the number of characters in the character sequence represented by this String object.
public boolean regionMatches(int toffset, String other, int ooffset, int len)
The index of the first character in this string.
The String object to be used in the comparison.
The index of the first character in other.
The length of the sub-sequences to be compared.
true if the sub-sequences are identical; otherwise false.
This method determines whether or not the specified sub-sequences in this String object and other are identical. The method returns false if toffset is negative, if ooffset is negative, if toffset+len is greater than the length of this string, or if ooffset+len is greater than the length of other. Otherwise, the method returns true if for all nonnegative integers k less than len it is true that:
this.charAt(toffset+k) == other.charAt(ooffset+k)
public boolean regionMatches(boolean ignoreCase, int toffset, String other, int ooffset, int len)
A boolean value that indicates whether case should be ignored.
The index of the first character in this string.
The String object to be used in the comparison.
The index of the first character in other.
The length of the sub-sequences to be compared.
true if the sub-sequences are identical; otherwise false. The ignoreCase argument controls whether or not case is ignored in the comparison.
This method determines whether or not the specified sub-sequences in this String object and other are identical. The method returns false if toffset is negative, if ooffset is negative, if toffset+len is greater than the length of this string, or if ooffset+len is greater than the length of other. Otherwise, if ignoreCase is false, the method returns true if for all nonnegative integers k less than len it is true that:
this.charAt(toffset+k) == other.charAt(ooffset+k)
If ignoreCase is true, the method returns true if for all nonnegative integers k less than len it is true that:
Character.toLowerCase(this.charAt(toffset+k)) == Character.toLowerCase(other.charAt(ooffset+k))
or:
Character.toUpperCase(this.charAt(toffset+k)) == Character.toUpperCase(other.charAt(ooffset+k))
The character to be replaced.
The replacement character.
A new String object that results from replacing every occurrence of oldChar in the string with newChar.
This method returns a new String object that results from replacing every occurrence of oldChar in this String object with newChar. If there are no occurrences of oldChar, the method simply returns this String object.
The String object prefix to be tested.
true if this string begins with the sequence of characters specified by prefix; otherwise false.
This method determines whether or not this String object begins with the specified prefix.
The String object prefix to be tested.
The index where the search is to begin.
true if this string contains the sequence of characters specified by prefix starting at the index toffset; otherwise false.
This method determines whether or not this String object contains the specified prefix at the index specified by toffset.
The index of the first character in the substring.
A new String object that contains the sub-sequence of this string that starts at beginIndex and extends to the end of the string.
If beginIndex is less than zero or greater than or equal to the length of the string.
This method returns a new String object that represents a sub-sequence of this String object. The sub-sequence consists of the characters starting at beginIndex and extending through the end of this String object.
The index of the first character in the substring.
The index after the last character in the substring.
A new String object that contains the sub-sequence of this string that starts at beginIndex and extends to the character at endindex-1.
If beginIndex or endIndex is less than zero or greater than or equal to the length of the string.
This method returns a new String object that represents a sub-sequence of this String object. The sub-sequence consists of the characters starting at beginIndex and extending through endIndex-1 of this String object.
A new char array that contains the same sequence of characters as this string.
This method returns a new char array that contains the same sequence of characters as this Stringobject. The length of the array is the same as the length of this String object.
A new String object that contains the characters of this string converted to lowercase.
This method returns a new String that represents a character sequence of the same length as this String object, but with each character replaced by its lowercase equivalent if it has one. If no character in the string has a lowercase equivalent, the method returns this String object.
New as of JDK 1.1
The Locale to use.
A new String object that contains the characters of this string converted to lowercase using the rules of the specified locale.
This method returns a new String that represents a character sequence of the same length as this String object, but with each character replaced by its lowercase equivalent if it has one according to the rules of the specified locale. If no character in the string has a lowercase equivalent, the method returns this String object.
This String object.
Object.toString()
This method returns this String object.
A new String object that contains the characters of this string converted to uppercase.
This method returns a new String that represents a character sequence of the same length as this String object, but with each character replaced by its uppercase equivalent if it has one. If no character in the string has an uppercase equivalent, the method returns this String object.
New as of JDK 1.1
The Locale to use.
A new String object that contains the characters of this string converted to uppercase using the rules of the specified locale.
This method returns a new String that represents a character sequence of the same length as this String object, but with each character replaced by its uppercase equivalent if it has one according to the rules of the specified locale. If no character in the string has an uppercase equivalent, the method returns this String object.
A new String object that represents the same character sequence as this string, but with leading and trailing whitespace and control characters removed.
If the first and last character in this String object are greater than '\u0020' (the space character), the method returns this String object. Otherwise, the method returns a new String object that contains the same character sequence as this String object, but with leading and trailing characters that are less than '\u0020'' removed.
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Method |
Inherited From |
Method |
Inherited From |
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clone() |
Object |
finalize() |
Object |
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getClass() |
Object |
notify() |
Object |
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notifyAll() |
Object |
wait() |
Object |
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wait(long) |
Object |
wait(long, int) |
Object |
Class, Character, Double, Float, Integer, Locale, Long, Object, StringBuffer, StringIndexOutOfBoundsException, UnsupportedEncodingException
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| StackOverflowError |  |
StringBuffer |
