Java String comparison

Introduction

To compare two strings for equality, use equals().

It has this general form: 

boolean equals(Object str)

Here, str is the String object being compared with the invoking String object.

It returns true if the strings contain the same characters in the same order, and false otherwise.

The comparison is case-sensitive.

To perform a comparison that ignores case differences, call equalsIgnoreCase().

It has this general form: 

boolean equalsIgnoreCase(String str)

Here is an example that demonstrates equals() and equalsIgnoreCase(): 

// Demonstrate equals() and equalsIgnoreCase().
public class Main {
  public static void main(String args[]) {
    String s1 = "Hello";
    String s2 = "Hello";
    String s3 = "Good-bye";
    String s4 = "HELLO";
    System.out.println(s1 + " equals " + s2 + " -> " +
                       s1.equals(s2));// w w  w  .  ja  va 2s . c  om
    System.out.println(s1 + " equals " + s3 + " -> " +
                       s1.equals(s3));
    System.out.println(s1 + " equals " + s4 + " -> " +
                       s1.equals(s4));
    System.out.println(s1 + " equalsIgnoreCase " + s4 + " -> " +
                       s1.equalsIgnoreCase(s4));
  }
}

String methods equals, equalsIgnoreCase, compareTo and regionMatches. 

public class Main 
{
   public static void main(String[] args)
   {/*w  w w. j a va 2  s.  c  o m*/
      String s1 = new String("hello"); // s1 is a copy of "hello"
      String s2 = "goodbye";
      String s3 = "Happy Birthday";
      String s4 = "happy birthday";

      System.out.printf(
         "s1 = %s\ns2 = %s\ns3 = %s\ns4 = %s\n\n", s1, s2, s3, s4);

      // test for equality
      if (s1.equals("hello"))  // true
         System.out.println("s1 equals \"hello\"");
      else
         System.out.println("s1 does not equal \"hello\""); 

      // test for equality with ==
      if (s1 == "hello")  // false; they are not the same object
         System.out.println("s1 is the same object as \"hello\"");
      else
         System.out.println("s1 is not the same object as \"hello\"");

      // test for equality (ignore case)
      if (s3.equalsIgnoreCase(s4))  // true
         System.out.printf("%s equals %s with case ignored\n", s3, s4);
      else
         System.out.println("s3 does not equal s4");

      // test compareTo
      System.out.printf(
         "\ns1.compareTo(s2) is %d", s1.compareTo(s2));
      System.out.printf(
         "\ns2.compareTo(s1) is %d", s2.compareTo(s1));
      System.out.printf(
         "\ns1.compareTo(s1) is %d", s1.compareTo(s1));
      System.out.printf(
         "\ns3.compareTo(s4) is %d", s3.compareTo(s4));
      System.out.printf(
         "\ns4.compareTo(s3) is %d\n\n", s4.compareTo(s3));

      // test regionMatches (case sensitive)
      if (s3.regionMatches(0, s4, 0, 5))
         System.out.println("First 5 characters of s3 and s4 match");
      else
         System.out.println(
            "First 5 characters of s3 and s4 do not match");

      // test regionMatches (ignore case)
      if (s3.regionMatches(true, 0, s4, 0, 5))
         System.out.println(
            "First 5 characters of s3 and s4 match with case ignored");
      else
         System.out.println(
            "First 5 characters of s3 and s4 do not match");
   } 
}



PreviousNext

Related