String Class in Java (original) (raw)

Last Updated : 01 May, 2025

A **string is a sequence of characters. In Java, objects of the **String class are immutable, which means they cannot be changed once created. In this article, we are going to learn about the **String class in Java.

**Example of String Class in Java:

Java `

// Java Program to Create a String import java.io.*;

class Geeks { public static void main (String[] args) {

      // String literal
    String s = "Geeks for Geeks String in Java";

      System.out.println(s);
}

}

`

Output

Geeks for Geeks String in Java

**Explanation:

The above program **creates a string using a literal and prints it.

Table of Content

• Creating a String
  • 1. Using String literal
  • 2. Using new keyword
• String Constructors in Java
• String Methods in Java
• Example of String Constructor and String Methods

Creating a String

There are **two ways to create string in Java:

1. Using String literal

String s = “GeeksforGeeks”;

2. Using new keyword

String s = new String (“GeeksforGeeks”);

Example of Creating String in Java

Java `

// Java Program to Create a String import java.io.*;

class Geeks { public static void main (String[] args) {

      // String literal
    String s1="String1";
      System.out.println(s1);
  
      // Using new Keyword 
      String s2= new String("String2");
      System.out.println(s2);
}

}

`

String Constructors in Java

Let us check these constructors using a example demonstrating the use of them.

Example String Constructor in Java

Java `

// Java Program to implement String Constructor import java.nio.charset.Charset;

class Geeks {

// Variables in Methods
static byte[] b_arr = {71, 101, 101, 107, 115};
static Charset cs = Charset.defaultCharset();
static char[] char_arr = {'G', 'e', 'e', 'k', 's'};
static int[] uni_code = {71, 101, 101, 107, 115};
static StringBuffer s_buffer = new StringBuffer("Geeks");
static StringBuilder s_builder = new StringBuilder("Geeks");

public static void main(String[] args) {
    
    // Method 1
    String s1 = new String(b_arr);
    System.out.println("Method 1: " + s1);
    System.out.println();

    // Method 2
    String s2 = new String(b_arr, cs);
    System.out.println("Method 2: " + s2);
    System.out.println();

    // This is alternative way for Method 2
    String s3 = new String(b_arr, Charset.forName("US-ASCII"));
    System.out.println("Method 2 Alternative: " + s3);
    System.out.println();

    // Method 3
    String s4 = new String(b_arr, 1, 3);
    System.out.println("Method 3: " + s4);
    System.out.println();

    // Method 4
    String s5 = new String(b_arr, 1, 3, cs);
    System.out.println("Method 4: " + s5);
    System.out.println();

    // This is alternative way for Method 4
    String s6 = new String(b_arr, 1, 4, Charset.forName("US-ASCII"));
    System.out.println("Method 4 Alternative: " + s6);
    System.out.println();

    // Method 5
    String s7 = new String(char_arr);
    System.out.println("Method 5: " + s7);
    System.out.println();

    // Method 6
    String s8 = new String(char_arr, 1, 3);
    System.out.println("Method 6: " + s8);
    System.out.println();

    // Method 7
    String s9 = new String(uni_code, 1, 3);
    System.out.println("Method 7: " + s9);
    System.out.println();

    // Method 8
    String s10 = new String(s_buffer);
    System.out.println("Method 8: " + s10);
    System.out.println();

    // Method 9
    String s11 = s_builder.toString();
    System.out.println("Method 9: " + s11);
    System.out.println();
}

}

`

Output

Method 1: Geeks

Method 2: Geeks

Method 2 Alternative: Geeks

Method 3: eek

Method 4: eek

Method 4 Alternative: eeks

Method 5: Geeks

Method 6: eek

Method 7: eek

Method 8: Geeks

Method 9: Geeks...

String Methods in Java

Example of String Constructor and String Methods

Below is the **implementation of string constructors and methods in Java.

Java `

// Java program to illustrate different // constructors and methods in String class import java.io.; import java.util.;

class Geeks { public static void main (String[] args) { String s= "GeeksforGeeks"; // or String s= new String ("GeeksforGeeks");

    // Returns the number of characters in the String
    System.out.println("String length = " + s.length());

    // Returns the character at ith index
    System.out.println("Character at 3rd position = "
                       + s.charAt(3));

    // Return the substring from the ith  index character
    // to end of string
    System.out.println("Substring " + s.substring(3));

    // Returns the substring from i to j-1 index
    System.out.println("Substring  = " + s.substring(2,5));

    // Concatenates string2 to the end of string1
    String s1 = "Geeks";
    String s2 = "forGeeks";
    System.out.println("Concatenated string  = " +
                        s1.concat(s2));

    // Returns the index within the string
    // of the first occurrence of the specified string
    String s4 = "Learn Share Learn";
    System.out.println("Index of Share " +
                       s4.indexOf("Share"));

    // Returns the index within the string of the
    // first occurrence of the specified string,
    // starting at the specified index
    System.out.println("Index of a  = " +
                       s4.indexOf('a',3));

    // Checking equality of Strings
    Boolean out = "Geeks".equals("geeks");
    System.out.println("Checking Equality  " + out);
    out = "Geeks".equals("Geeks");
    System.out.println("Checking Equality  " + out);

    out = "Geeks".equalsIgnoreCase("gEeks ");
    System.out.println("Checking Equality " + out);

    // If ASCII difference is zero then 
    // the two strings are similar
    int out1 = s1.compareTo(s2);
    System.out.println("the difference between ASCII value is="+out1);
    
    // Converting cases
    String w1 = "GeeKyMe";
    System.out.println("Changing to lower Case " +
                        w1.toLowerCase());

    // Converting cases
    String w2 = "GeekyME";
    System.out.println("Changing to UPPER Case " +
                        w2.toUpperCase());

    // Trimming the word
    String w4 = " Learn Share Learn ";
    System.out.println("Trim the word " + w4.trim());

    // Replacing characters
    String str1 = "feeksforfeeks";
    System.out.println("Original String " + str1);
    String str2 = "feeksforfeeks".replace('f' ,'g') ;
    System.out.println("Replaced f with g -> " + str2);
}

}

`

**Output:

For Set -2, you can refer: Java.lang.String class in Java | Set 2