Tutorials Java Java String Examples

Java String Examples

1. String Length and Trim

Code snippet explains the usage of String class length and trim() method.

  • The length() method returns the length of this string.
  • The trim() method returns a copy of the string, with leading and trailing whitespace omitted.
import java.util.Scanner;

public class StringExampleTwo {
    public static void main(String args[]) {
        
        Scanner scanner= new Scanner(System.in);
        System.out.println("Enter a string with space");
        
        String s1 = scanner.nextLine();
        System.out.println("s1 = " + s1);

        // Display String Length
        System.out.println("The length of s1 is: " + s1.length());

        // Removing extra spaces from s1
        String s2 = s1.trim();

        System.out.println("s2 = " + s2);
        System.out.println("The length of s2 is: " + s2.length());
    }

}

Output

String length and trim string in java

2. String Equality Check

Sample program to test String Equality in Java using equals to () operator and String.equals() method.

public class StringEqualsTest {
    public static void main(String[] args) {
        String str1 = "hello";
        String str2 = str1;
        String str3 = new String("hellp");
        String str4 = new String("hello 2");
        String str5 = "hello";
        
        System.out.println("Comparison using == : " + (str1 == str5));
        System.out.println("Comparison using == : " + (str1 == str2));
        System.out.println("Comparison Using equals() method : " + str1.equals(str2));
        System.out.println("Comparison using == : " + (str3 == str4));
        System.out.println("Comparison Using equals() method : " + str3.equals(str4));
    }
}

Output
How to Test String Equality in Java

3. String Concatenation

Sample Java program to concatenate two strings using plus (+) concatenation operator.

public class StringConcatination {
    public static void main(String args[]) {
        String str1 = "Hello";
        String str2 = "JavaTechig";

        // Concatenation
        String str3 = str1.concat(str2);

        System.out.println("str1 = " + str1);
        System.out.println("str2 = " + str2);
        System.out.println("str3 = " + str3);

        String str4 = "Hello";

        // checking equals
        if (str4.equals(str1)) {
            System.out.println("str4 is equal to str1");
        } else {
            System.out.println("str4 is not equal to str1");
        }

    }
}

Output

String Concatenation Test in Java

4. Change Uppercase to Lowercase

Quick Java code snippet to change the case of a String in Java. It uses toUpperCase() and toLowerCase() methods present in java.lang.String class to convert the case.

public class StringCase {
    public static void main(String args[]) {
        String str = "This code snippet is brought you by Java Techhig";

        // toUpperCase() method converts the complete string in upper case
        String strUpper = str.toUpperCase();

        // toLowerCase() method converts the complete string in lower case
        String strLower = str.toLowerCase();

        // printing changed case string
        System.out.println("Upper Case: " + strUpper);
        System.out.println("Lower Case: " + strLower);
    }
}

Output
Change Case of a String in Java

5. Reverse String

import java.util.Scanner;

class ReverseString
{
   public static void main(String args[])
   {
      String original, reverse = "";
      Scanner scanner = new Scanner(System.in);
 
      System.out.println("Enter a string to reverse");
      original = scanner.nextLine();
      int length = original.length();
 
      for ( int i = length - 1 ; i >= 0 ; i-- ){
         reverse = reverse + original.charAt(i);
      }
 
      System.out.println("Reverse of entered string is: "+reverse);
   }
}

Output
Reverse String in java

6. Reverse String using Recursion

import java.util.Scanner;

public class StringRecursiveReverse {
    public String reverseString(String str) {
        String reverse = "";
        if (str.length() == 1) {
            return str;
        } else {
            reverse += str.charAt(str.length() - 1) + reverseString(str.substring(0, str.length() - 1));
            return reverse;
        }
    }

    public static void main(String args[]) {
        StringRecursiveReverse srr = new StringRecursiveReverse();
        Scanner scanner = new Scanner(System.in);
        System.out.println("Enter a string to reverse");
        String original = scanner.nextLine();

        System.out.println("Result: " + srr.reverseString(original));
    }
}

Output
Reverse Java String using recursive method

7. Compare Strings

import java.util.Scanner;

class CompareStrings {
     public static void main(String args[]) {
      String str1, str2;
      Scanner in = new Scanner(System.in);
      System.out.println("Enter the first string");
      str1 = in .nextLine();
    
      System.out.println("Enter the second string");
      str2 = in .nextLine();
    
      if (str1.compareTo(str2) > 0){
            System.out.println("First string is greater than second."); 
      } else if (str1.compareTo(str2) < 0){
            System.out.println("First string is smaller than second."); 
      } else{
            System.out.println("Both strings are equal.");
      }
    }
}
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