Core Java Tutorial

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Java has Following Features/Characteristics

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Operator on Integer and Separators in Java Programming

Java Control Flow of Statements

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Array in Java

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Two Dimensional Array Program

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String args Types in Java

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Math Class Function and Constant

Math Class all Function used in a program

Enumerated Types in Java

Object Oriented Programming v/s Procedural Programming

Object Oriented Programming Concepts in Java

Introduction to Class,Object and Method in Java

Class Declaration in Java

Class & Objects in java

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Polymorphism in Java

Runtime polymorphism (dynamic binding or method overriding)

how to convert a HashSet to Array using collections in java

how to convert a HashSet to Array using collections in java

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In this example we shall see how can we convert a HashSet to a linear array.

For creating a HashSet we have to import the java.util package in which the HashSet class is defined. In this example we have created a class name CollectionExample in which we created a HashSet and added various elements to it.
 In this example we have created a HashSet and added some elements to it. Then we have created an Integer array of same size as that of the HashSet by using the following statement,
Integer[] array= new Integer[set.size()];
where set is the object of the HashSet.

After creating an array we have used the toArray(Anytypearray[] array) on the object of the HashSet, which is demonstrated by the following line in the example,

array=set.toArray(array);

In the given example we have created a HashSet having the integral values in it. Furthermore we have created an array which is used for containg the elements returned by invoking the toArray(Anytypearray[] array) method on the HashSet object set.

 
package r4r.co.in;
import java.util.*;


public class CollectionExample {

/**
* @param args
*/
public static void main(String[] args)
{
// TODO Auto-generated method stub



HashSet<Integer> set=new HashSet<Integer>(); // creating a HashSet named set
set.add(1); // adding elements to the HashSet
set.add(3);
set.add(4);
set.add(5);
set.add(7);
set.add(1);
set.add(4);
set.add(7);
//Iterator<Integer> itr=set.iterator();
System.out.println("The contents of the set are:"); //displaying the contents of the HashSet
System.out.println(set);

Integer[] array= new Integer[set.size()]; // creating an Integer array of same size as that of the HashSet set
array=set.toArray(array); // converting the set to the Array
System.out.println("The contents of the array are as follows: ");
for(int i=0;i<array.length;i++)
{
System.out.println(array[i]); // displaying the content of the array thus created
}


}


}


The output of the above code is the following one,

The contents of the set are:
[1, 3, 4, 5, 7]
The contents of the array are as follows:
1
3
4
5
7

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