Java/Data Type/String equal

Check string for equality

 
 
public class Main {
  public static void main(String[] args) {
    String s1 = "Hello World";
    String s2 = new String("Hello World");
    if (s1.equals(s2)) {
      System.out.println("String is equal");
    } else {
      System.out.println("String is unequal");
    }
    if (s1 == s2) {
      System.out.println("String is equal");
    } else {
      System.out.println("String is unequal");
    }
  }
}

Determine whether a string is a palindrome?

 
 
public class Main {
  static boolean isPalindrome(String text) {
    System.out.println("Original text = " + text);
    String reverse = new StringBuilder(text).reverse().toString();
    System.out.println("Reverse text  = " + reverse);
    return text.equalsIgnoreCase(reverse);
  }
  public static void main(String[] args) {
    String text = "Sator Arepo Tenet Opera Rotas";
    System.out.println("Is Palindrom: " + isPalindrome(text));
  }
}

String: equal

 
/*
 * Copyright (c) Ian F. Darwin, http://www.darwinsys.ru/, 1996-2002.
 * All rights reserved. Software written by Ian F. Darwin and others.
 * $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS""
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 * 
 * Java, the Duke mascot, and all variants of Sun"s Java "steaming coffee
 * cup" logo are trademarks of Sun Microsystems. Sun"s, and James Gosling"s,
 * pioneering role in inventing and promulgating (and standardizing) the Java 
 * language and environment is gratefully acknowledged.
 * 
 * The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
 * inventing predecessor languages C and C++ is also gratefully acknowledged.
 */
public class Equality {
  public static void main(String[] args) { 
    new Equality().run();
  }
  public void run() {
    String x = "hello";
    String y = "hello";
  
    // Assuming Equality uses a String constant, this prints true,true
    compare(x, y);
    // A "new String" is uniquely created, so this prints false, true
    compare(x, new String(y));
    // The substring operator creates a new String, prints false, true
    compare(x, "hello world".substring(0, 5));
    // The intern() operator returns a string from the pool of unique
    // strings, so this should print true, true.
    compare(x, new String(x).intern());
  }
  public void compare(String s1, String s2) {
    System.out.print("==:       ");
    System.out.println(s1 == s2);
    System.out.println(".equals():" + s1.equals(s2));
    System.out.println(); 
  }
}