Remove element from certain array using JAVA?

Question

Problem: Given an array and a value, remove all instances of that value in place and return the new length. The order of elements can be changed. It doesn't matter what you leave beyond the new length.

I want to solve this question by using JAVA ArrayList. And by code is listed as follows:

import java.util.ArrayList;
import java.util.Arrays;


public class removeElement {

/**
 * @param args
 */
public int removeElement(int[] A, int elem) {

    int length = 0;
    ArrayList<Integer> al = new ArrayList<Integer>();
    Arrays.sort(A);
    //add elements in A to al
    for(int i:A){
        al.add(i);
    }
    //Remember arraylist's remove() is to remove first occurance of elements. 
    if(al.contains(elem)&&al.size() == 1){
        return 0;
    }
    while(al.contains(elem)){
        al.remove(elem);
    }
    length = al.size();
    return length;

}
public static void main(String[] args) {
    // TODO Auto-generated method stub
    removeElement re = new removeElement();
    int[] A = {3, 3};
    int element = 3;
    System.out.println(re.removeElement(A, element));

}

}

The result shows that:

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 3, Size: 2
    at java.util.ArrayList.rangeCheck(ArrayList.java:571)
    at java.util.ArrayList.remove(ArrayList.java:412)
    at removeElement.removeElement(removeElement.java:24)
    at removeElement.main(removeElement.java:35)

Can I use JAVA ArrayList to solve this problem? Or should I solve it in another way? Waiting for your reply. Thanks a lot!

even though it would not be the answer to your particular question, I would rather use Predicates for this purpose stackoverflow.com/questions/2312849/… — MatthiasLaug
– MatthiasLaug, Commented Mar 16, 2014 at 16:39

RMachnik · Accepted Answer · 2014-03-16 16:40:14Z

5

You can do it simpler.

public int[] removeElement(int[] input, int deleteMe) {
    List<Integer> result = new LinkedList();

    for(int i=0;input.length;i++)
        if(deleteMe!=input[i])
            result.add(input[i]);

    return result.toArray(input);
}

answered Mar 16, 2014 at 16:40

RMachnik

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2 Comments

tonymiao Over a year ago

It is really efficient!

RMachnik Over a year ago

You're welcome, so it might be marked as proper answer maybe ;)

Abimaran Kugathasan · Accepted Answer · 2014-03-16 16:44:20Z

2

Since there are two overloaded remove() methods in ArrayList which one accepting int parameter as an index of the object and the other one accept Object as parameter to remove.

You have use wrapper object to remove that element which is int. Otherwise, the overloaded remove(int index) will be called and you don't have any element at index of 3, So, you got IndexOutOfBoundsException

while(al.contains(elem)){
   al.remove(new Integer(elem));
}

edited Mar 16, 2014 at 16:44

answered Mar 16, 2014 at 16:38

Abimaran Kugathasan

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