Java String Methods

In Java, a String represents a sequence of characters used for storing and manipulating text. It is immutable and provides many built-in methods for operations like concatenation, comparison, and manipulation.

Java

public class Geeks{
    public static void main(String[] args) {
        String str = "GeeksforGeeks";

        System.out.println("Length: " + str.length());  
        System.out.println("Uppercase: " + str.toUpperCase());
        System.out.println("Substring: " + str.substring(2, 6));
    }
}

Output

Length: 13
Uppercase: GEEKSFORGEEKS
Substring: eksf

Commonly Used Java String Methods.

Java provides a rich set of String methods that help perform various operations like comparison, searching, modification of string. Let's Understand one by one.

1. int length() Method

This method provides the total count of characters in the string.

Java

public class Geeks {
    public static void main(String[] args) {
        String s = "Hello, World!";
        System.out.println(s.length());
    }
}

Output

2. charAt(int i) Method

This method returns the character at ith index.

Java

public class Geeks {
    public static void main(String[] args) {
        String s = "Hello, World!";
        System.out.println(s.charAt(7));
    }
}

Output

3. String substring(int i) Method

This method return the substring from the ith index character to end.

Java

public class Geeks {
    public static void main(String[] args) {
        String s = "Hello, World!";
        System.out.println(s.substring(7));
    }
}

Output

World!

4. String substring(int i, int j) Method

This method returns the substring from i to j-1 index.

Java

public class Geeks {
    public static void main(String[] args) {
        String s = "Hello, World!";
        System.out.println(s.substring(7, 12));
    }
}

Output

World

5. String concat( String str) Method

This method appends the given string to the end of the current string.

Java

public class Geeks {
    public static void main(String[] args) {
        String s = "Hello, World!";
        System.out.println(s.concat("!!!"));
    }
}

Output

Hello, World!!!!

6. int indexOf(String s) Method

This method returns the index within the string of the first occurrence of the specified string. If the specified string s is not found in the input string, the method returns -1 by default.

Java

public class Geeks {
    public static void main(String[] args) {
        String s = "Hello, World!";
        System.out.println(s.indexOf("World"));
    }
}

Output

7. int indexOf(String s, int i) Method

This method returns the index within the string of the first occurrence of the specified string, starting at the specified index.

Java

public class Geeks {
    public static void main(String[] args) {
        String str = "Hello, World!";
        System.out.println(str.indexOf("l", 4));
    }
}

Output

8. int lastIndexOf(String s) Method

This method returns the index within the string of the last occurrence of the specified string. If the specified string s is not found in the input string, the method returns -1 by default.

Java

public class Geeks {
    public static void main(String[] args) {
        String s = "Hello, World!";
        System.out.println(s.lastIndexOf("l"));
    }
}

Output

9. boolean equals(Object otherObj) Method

This method compares this string to the specified object.

Java

public class Geeks {
    public static void main(String[] args) {
        String s = "Hello, World!";
        System.out.println(s.equals("Hello, World!"));
    }
}

Output

true

10. boolean equalsIgnoreCase(String anotherString) Method

This method checks if two strings are equal, without considering letter case.

Java

public class Geeks {
    public static void main(String[] args) {
        String s = "Hello, World!";
        System.out.println(s.equalsIgnoreCase("hello, world!"));
    }
}

Output

true

11. int compareTo(String anotherString) Method

This method compares two string lexicographically.

Java

public class Geeks {
    public static void main(String[] args) {
        String s = "Hello, World!";
        System.out.println(s.compareTo("Hello, Java!"));
    }
}

Output

12. int compareToIgnoreCase(String anotherString) Method

This method compares two string lexicographically, ignoring case considerations.

Java

public class Geeks {
    public static void main(String[] args) {
        String s = "Hello, World!";
        System.out.println(s.compareToIgnoreCase("hello, java!"));
    }
}

Output

13. String toLowerCase() Method

This method converts all the characters in the String to lower case.

Java

public class Geeks {
    public static void main(String[] args) {
        String s = "Hello, World!";
        System.out.println(s.toLowerCase());
    }
}

Output

hello, world!

14. String toUpperCase() Method

This method converts all the characters in the String to upper case.

Java

public class Geeks {
    public static void main(String[] args) {
        String s = "Hello, World!";
        System.out.println(s.toUpperCase());
    }
}

Output

HELLO, WORLD!

15. String trim() Method

This method returns the copy of the String, by removing whitespaces at both ends. It does not modify the whitespace characters present between the text.

Java

public class Geeks {
    public static void main(String[] args) {
        String s = "   Hello, Trim!   ";
        System.out.println("'" + s.trim() + "'");
    }
}

Output

'Hello, Trim!'

16. String replace(char oldChar, char newChar) Method

This method returns a new string where all instances of oldChar are replaced by newChar.

Java

public class Geeks {
    public static void main(String[] args) {
        String s = "Hello, World!";
        System.out.println(s.replace('l', 'x'));
    }
}

Output

Hexxo, Worxd!

17. boolean contains(CharSequence sequence) Method

This method returns true if string contains the given string.

Java

public class Geeks {
    public static void main(String[] args) {
        String s = "Hello, World!";
        System.out.println(s.contains("World"));
    }
}

Output

true

18. char[] toCharArray() Method

This method converts the string into a new character array.

Java

public class Geeks {
    public static void main(String[] args) {
        String str = "Hello";
        char[] chars = str.toCharArray();
        for(char c : chars) {
            System.out.print(c + " ");
        }
    }
}

Output

H e l l o

19. boolean startsWith(String prefix) Method

This method returns true if string starts with this prefix.

Java

public class Geeks {
    public static void main(String[] args) {
        String s = "Hello, World!";
        System.out.println(s.startsWith("Hello"));
    }
}

Output

true

Common String Methods in Java

String Methods	Description
int length()	Returns the number of characters in the String.
char charAt(int i)	Returns the character at ith index.
String substring (int i)	Return the substring from the ith index character to end.
String substring (int i, int j)	Returns the substring from i to j-1 index.
String concat( String str)	Concatenates specified string to the end of this string.
int indexOf (String s)	Finds the position of the first occurrence of the given substring within the main string. If the specified string s is not found in the input string, the method returns -1 by default.
int indexOf (String s, int i)	Returns the index within the string of the first occurrence of the specified string, starting at the specified index.
int lastIndexOf( String s)	Returns the index within the string of the last occurrence of the specified string. If the specified string s is not found in the input string, the method returns -1 by default.
boolean equals( Object otherObj)	Compares this string to the specified object.
boolean equalsIgnoreCase (String anotherString)	Compares string to another string, ignoring case considerations.
int compareTo( String anotherString)	Compares two string lexicographically.
int compareToIgnoreCase( String anotherString)	Compares two string lexicographically, ignoring case considerations. Note: In this case, it will not consider case of a letter (it will ignore whether it is uppercase or lowercase).
String toLowerCase()	Converts all the characters in the String to lower case.
String toUpperCase()	Converts all the characters in the String to upper case.
String trim()	Returns the copy of the String, by removing whitespaces at both ends. Whitespace characters between words remain unchanged.
String replace (char oldChar, char newChar)	Generates a new string where every instance of oldChar is substituted with newChar. Note: s1 is still feeksforfeeks and s2 is geeksgorgeeks
boolean contains(CharSequence sequence)	Returns true if string contains the given string.
Char[] toCharArray()	Converts this String to a new character array.
boolean startsWith(String prefix)	Return true if string starts with this prefix.

Commonly Used Java String Methods.

Common String Methods in Java

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