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Java Tutorial : Java String Comparison

CompareByEqualsDemo.java

public class CompareByEqualsDemo
{

    public static void main(String[] args)
    {
        String s1 = "Peter";
        String s2 = "Peter";
        String s3 = new String("Peter");
        String s4 = "Dave";
        System.out.println(s1.equals(s2));// true
        System.out.println(s1.equals(s3));// true
        System.out.println(s1.equals(s4));// false
    }

}

Output

true
true
false

CompareByEqualsIgnoreCaseDemo.java

public class CompareByEqualsIgnoreCaseDemo
{

    public static void main(String[] args)
    {
        String s1 = "peter";
        String s2 = "PETER";

        System.out.println(s1.equals(s2));// false
        System.out.println(s1.equalsIgnoreCase(s2));// true

    }

}

Output

false
true

CompareByDemo.java

public class CompareByDemo
{

    public static void main(String[] args)
    {
        String s1 = "Peter";
        String s2 = "Peter";
        String s3 = new String("Peter");

        /*
         * true (because both refer to same instance)
         */
        System.out.println(s1 == s2);

        /*
         * false(because s3 refers to instance created in
         * nonpool)
         */
        System.out.println(s1 == s3);

    }

}

Output

true
false

public class CompareByCompareToDemo
{

    public static void main(String[] args)
    {
        String s1 = "Sachin";
        String s2 = "Sachin";
        String s3 = "Ratan";
        
        System.out.println(s1.compareTo(s2));// 0

        /*
         * 1(because s1>s3)
         */
        System.out.println(s1.compareTo(s3));
        /*
         * -1(because s3 < s1 )
         */
        System.out.println(s3.compareTo(s1));

    }

}