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String Class

A String is a sequence of characters. In Java, objects of String are immutable which means a constant and cannot be changed once created.

  • Immutable: Cannot be changed once created.
  • Package: java.lang.String
  • Hierarchy: Extends Object, Implements Serializable, CharSequence, Comparable.

Ways to Create String Object

1. Using Literal

Stored in the String Constant Pool (SCP). Memory efficient.

String str1 = "Delhi"; String str2 = "Mumbai"; String str3 = "Jaladhi Naga Vijay";

2. Using `new` Keyword

Stored in Heap memory. Creates a new object every time.

String str1 = new String("New York"); String str2 = new String("California"); String str3 = new String("San Jose");

Fields in String Class

Field Name Description
CASE_INSENSITIVE_ORDER A Comparator that orders String objects as by compareToIgnoreCase.

Methods in String Class

Method Signature Description
charAt(int index) Returns the char value at the specified index.
codePointAt(int index) Returns the character (Unicode code point) at the specified index.
codePointCount(int beginIndex, int endIndex) Returns the number of Unicode code points in the specified text range.
compareTo(String anotherString) Compares two strings lexicographically.
compareToIgnoreCase(String str) Compares two strings lexicographically, ignoring case differences.
concat(String str) Concatenates the specified string to the end of this string.
contains(CharSequence s) Returns true if and only if this string contains the specified sequence of char values.
contentEquals(CharSequence cs) Compares this string to the specified CharSequence.
contentEquals(StringBuffer sb) Compares this string to the specified StringBuffer.
copyValueOf(char[] data) Returns a String that represents the character sequence in the array specified.
copyValueOf(char[] data, int offset, int count) Returns a String that represents the character sequence in the array specified.
endsWith(String suffix) Tests if this string ends with the specified suffix.
equals(Object anObject) Compares this string to the specified object.
equalsIgnoreCase(String anotherString) Compares this String to another String, ignoring case considerations.
format(Locale l, String format, Object... args) Returns a formatted string using the specified locale, format string, and arguments.
format(String format, Object... args) Returns a formatted string using the specified format string and arguments.
getBytes() Encodes this String into a sequence of bytes using the platform's default charset.
getBytes(Charset charset) Encodes this String into a sequence of bytes using the given charset.
getBytes(int srcBegin, int srcEnd, byte[] dst, int dstBegin) Deprecated Does not properly convert characters into bytes. Use getBytes() instead.
getBytes(String charsetName) Encodes this String into a sequence of bytes using the named charset.
getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin) Copies characters from this string into the destination character array.
hashCode() Returns a hash code for this string.
indexOf(int ch) Returns the index within this string of the first occurrence of the specified character.
indexOf(int ch, int fromIndex) Returns the index of the first occurrence of the specified character, starting the search at the specified index.
indexOf(String str) Returns the index within this string of the first occurrence of the specified substring.
indexOf(String str, int fromIndex) Returns the index of the first occurrence of the specified substring, starting at the specified index.
intern() Returns a canonical representation for the string object.
isEmpty() Returns true if, and only if, length() is 0.
lastIndexOf(int ch) Returns the index within this string of the last occurrence of the specified character.
lastIndexOf(int ch, int fromIndex) Returns the index of the last occurrence of the specified character, searching backward.
lastIndexOf(String str) Returns the index within this string of the last occurrence of the specified substring.
lastIndexOf(String str, int fromIndex) Returns the index of the last occurrence of the specified substring, searching backward.
length() Returns the length of this string.
matches(String regex) Tells whether or not this string matches the given regular expression.
offsetByCodePoints(int index, int codePointOffset) Returns the index within this String that is offset from the given index by codePointOffset code points.
regionMatches(boolean ignoreCase, int toffset, String other, int ooffset, int len) Tests if two string regions are equal.
regionMatches(int toffset, String other, int ooffset, int len) Tests if two string regions are equal.
replace(char oldChar, char newChar) Returns a new string resulting from replacing all occurrences of oldChar in this string with newChar.
replace(CharSequence target, CharSequence replacement) Replaces each substring of this string that matches the literal target sequence with the specified literal replacement sequence.
replaceAll(String regex, String replacement) Replaces each substring of this string that matches the given regular expression with the given replacement.
replaceFirst(String regex, String replacement) Replaces the first substring of this string that matches the given regular expression with the given replacement.
split(String regex) Splits this string around matches of the given regular expression.
split(String regex, int limit) Splits this string around matches of the given regular expression with a limit.
startsWith(String prefix) Tests if this string starts with the specified prefix.
startsWith(String prefix, int toffset) Tests if the substring of this string beginning at the specified index starts with the specified prefix.
subSequence(int beginIndex, int endIndex) Returns a new character sequence that is a subsequence of this sequence.
substring(int beginIndex) Returns a new string that is a substring of this string.
substring(int beginIndex, int endIndex) Returns a new string that is a substring of this string.
toCharArray() Converts this string to a new character array.
toLowerCase() Converts all of the characters in this String to lower case using the rules of the default locale.
toLowerCase(Locale locale) Converts all of the characters in this String to lower case using the rules of the given Locale.
toString() This object (which is already a string!) is itself returned.
toUpperCase() Converts all of the characters in this String to upper case using the rules of the default locale.
toUpperCase(Locale locale) Converts all of the characters in this String to upper case using the rules of the given Locale.
trim() Returns a copy of the string, with leading and trailing whitespace omitted.
valueOf(boolean b) Returns the string representation of the boolean argument.
valueOf(char c) Returns the string representation of the char argument.
valueOf(char[] data) Returns the string representation of the char array argument.
valueOf(char[] data, int offset, int count) Returns the string representation of a specific subarray of the char array argument.
valueOf(double d) Returns the string representation of the double argument.
valueOf(float f) Returns the string representation of the float argument.
valueOf(int i) Returns the string representation of the int argument.
valueOf(long l) Returns the string representation of the long argument.
valueOf(Object obj) Returns the string representation of the Object argument.