Java For each loop object assignment is not working

Question

public class A{

    int val;    
    public A(int val){
        this.val = val;
    }

    public void print() {
        System.out.println(val);

    }


    public static void main(String args[]){

        A[] aList = new A[10];
        int temp =1;

        for(A a : aList){
            a = new A(temp++);          
        }

        for(A a : aList){
            a.print();;         
        }

    }


}

Getting Exception in thread "main" java.lang.NullPointerException at A.main(A.java:28) aList address space Class A objects are stored but again iterate unable to get stored objects, where are the objects stored ?

Eran · Accepted Answer · 2014-12-23 14:14:56Z

14

a is a local variable of the for loop, so assigning to it doesn't affect the elements of the aList array.

You should use a regular for loop to initialize the array :

    for(int i = 0; i < aList.length; i++){
        aList[i] = new A(temp++);          
    }

answered Dec 23, 2014 at 14:14

Eran

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Comments

Kevin Workman · Accepted Answer · 2014-12-23 14:15:34Z

3

That's not how an enhanced for works. Use a standard for loop instead:

for(int i = 0; i < aList.length; i++){
   aList[i] = new A(temp++);          
}

The enhanced for uses an Iterator to loop through every element of the array. And since your array only contains null values, you're getting a NullPointerException.

answered Dec 23, 2014 at 14:15

Kevin Workman

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