Метод System.identityHashCode () в Java с примерами

Java.lang.System.identityHashCode () - это метод, который используется для возврата одного и того же хэш-кода для любого заданного объекта, который возвращается методом по умолчанию hashCode (). Кроме того, для каждого хэш-кода с нулевой ссылкой возвращается ноль.

Points to be Remembered:

• By default, every class either implicitly or explicitly provides a hashCode() method
• A hashcode is generally a number generated from any object which allows objects to be stored or retrieved very quickly in a Hashtable.
• In Java, hashCode() by default is a native method, which means that the method has a modifier ‘native’, when it is implemented directly in the native code in the JVM.
• Used to digest all the data stored in an instance of the class into a single hash value i.e., a 32-bit signed integer.

  Syntax :

  public static int identityHashCode(Object x)

  Parameters: The parameter x is of the type of the Hash and refers to the hashCode that is needed to be calculated.

  Return Value: This method returns the hashCode.

  Below programs illustrate the use of java.lang.System.identityHashCode() method.

  Program 1:

  // Java program to demonstrate working // of java.lang.System.identityHashCode() method. import java.lang.*; import java.io.*;    public class SystemCode1 {        public static void main(String[] args) throws Exception     {            File filename1 = new File("Welcome");         File filename2 = new File("Welcome");         File filename3 = new File("Geek");         File filename4 = new File("World");            // Returns the HashCode         int returnvalue1 = System.identityHashCode(filename1);         System.out.println(returnvalue1);            // Returns different HashCode for same filename         int returnvalue2 = System.identityHashCode(filename2);         System.out.println(returnvalue2);            // Returns the HashCode         int returnvalue3 = System.identityHashCode(filename3);         System.out.println(returnvalue3);            // Returns the HashCode         int returnvalue4 = System.identityHashCode(filename4);         System.out.println(returnvalue4);     } }

  Output:

  589431969
  1252169911
  2101973421
  685325104
  

  Explanation:
  In the above program, different hashcode or number are generated from an object even if they have the same name. Like here we can see first two terms are same i.e., “Welcome”, but we have two different values, which are

  • 589431969
  • 1252169911

  respectively for first and second Welcome

  Program 2:

  // Java program to demonstrate working // of java.lang.System.identityHashCode() method. import java.lang.*; import java.io.*;    public class SystemCode2 {        public static void main(String[] args) throws Exception     {            File filename1 = new File("10");         File filename2 = new File("shyam");         File filename3 = new File("s12");         File filename4 = new File("s12");            // Returns the HashCode         int returnvalue1 = System.identityHashCode(filename1);         System.out.println(returnvalue1);            // Returns the HashCode         int returnvalue2 = System.identityHashCode(filename2);         System.out.println(returnvalue2);            // Returns different HashCode for same filename         int returnvalue3 = System.identityHashCode(filename3);         System.out.println(returnvalue3);            // Returns different HashCode for same filename         int returnvalue4 = System.identityHashCode(filename4);         System.out.println(returnvalue4);     } }

  Output:

  589431969
  1252169911
  2101973421
  685325104
  

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