Java Hashtable clone() Method

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Description

The Java Hashtable clone() method is used to create a shallow copy of this hashtable.

Declaration

Following is the declaration for java.util.Hashtable.clone() method.

public Object clone()

Parameters

NA

Return Value

The method call returns a clone of the hashtable.

Exception

NA

Cloning a HashTable of Integer, Integer Pair Example

The following example shows the usage of Java Hashtable clone() method to get a shallow copy of a Hashtable. We've created two Hashtable objects of Integer,Integer pairs. Then few entries are added to one table, another table is populated using clone() method and then both hashtables are printed.

package com.tutorialspoint;

import java.util.Hashtable;

public class HashtableDemo {
   public static void main(String args[]) {
      
      // create two hash hashtables
      Hashtable<Integer, Integer> hashtable1 = new Hashtable<>();
      Hashtable<Integer, Integer> hashtable2 = new Hashtable<>();

      // populate 1st table
      hashtable1.put(1, 1);
      hashtable1.put(2, 2);
      hashtable1.put(3, 3); 

      // clone 1st table
      hashtable2 = (Hashtable)hashtable1.clone();

      System.out.println("1st Hashtable: " + hashtable1);
      System.out.println("Cloned 2nd Hashtable: " + hashtable2);   
   }    
}

Output

Let us compile and run the above program, this will produce the following result.

1st Hashtable: {3=3, 2=2, 1=1}
Cloned 2nd Hashtable: {3=3, 2=2, 1=1}

Cloning a HashTable of Integer, String Pair Example

The following example shows the usage of Java Hashtable clone() method to get a shallow copy of a Hashtable. We've created two Hashtable objects of Integer,String pairs. Then few entries are added to one table, another table is populated using clone() method and then both hashtables are printed.

package com.tutorialspoint;

import java.util.Hashtable;

public class HashtableDemo {
   public static void main(String args[]) {
      
      // create two hash hashtables
      Hashtable<Integer, String> hashtable1 = new Hashtable<>();
      Hashtable<Integer, String> hashtable2 = new Hashtable<>();

      // populate 1st table
      hashtable1.put(1, "A");
      hashtable1.put(2, "B");
      hashtable1.put(3, "C"); 

      // clone 1st table
      hashtable2 = (Hashtable)hashtable1.clone();

      System.out.println("1st Hashtable: " + hashtable1);
      System.out.println("Cloned 2nd Hashtable: " + hashtable2);   
   }    
}

Output

Let us compile and run the above program, this will produce the following result.

1st Hashtable: {3=C, 2=B, 1=A}
Cloned 2nd Hashtable: {3=C, 2=B, 1=A}

Cloning a HashTable of Integer, Object Pair Example

The following example shows the usage of Java Hashtable clone() method to get a shallow copy of a Hashtable. We've created two Hashtable objects of Integer,Student pairs. Then few entries are added to one table, another table is populated using clone() method and then both hashtables are printed.

package com.tutorialspoint;

import java.util.Hashtable;

public class HashtableDemo {
   public static void main(String args[]) {
      
      // create two hash hashtables
      Hashtable<Integer, Student> hashtable1 = new Hashtable<>();
      Hashtable<Integer, Student> hashtable2 = new Hashtable<>();

      // populate hash table
      hashtable1.put(1, new Student(1, "Julie"));
      hashtable1.put(2, new Student(2, "Robert"));
      hashtable1.put(3, new Student(3, "Adam"));

      // clone 1st table
      hashtable2 = (Hashtable)hashtable1.clone();

      System.out.println("1st Hashtable: " + hashtable1);
      System.out.println("Cloned 2nd Hashtable: " + hashtable2);   
   }    
}
class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
}

Output

Let us compile and run the above program, this will produce the following result.

1st Hashtable: {3=[ 3, Adam ], 2=[ 2, Robert ], 1=[ 1, Julie ]}
Cloned 2nd Hashtable: {3=[ 3, Adam ], 2=[ 2, Robert ], 1=[ 1, Julie ]}