How can I remove object in one array from another array?

Question

Let's say I have these lists:

List<Integer> numbersA=new ArrayList<Integer>();
List<Integer> numbersB=new ArrayList<Integer>();

"Numbers A" is [1,3,4,7,5,2] (There are no duplicate numbers) and "Numbers B" is: [13,32,533,3,4,2]

So the method will remove "Numbers A" from "Numbers B",and "Numbers B" will be: [13,32,533]

Traverse through one arraylist and try to remove items from the other. — Vucko, Jul 24 '16 at 15:11
Your example is wrong, you can't have a `List` with primitive types like `int`. — Loris Securo, Jul 24 '16 at 15:16

score 2 · Accepted Answer · edited Jun 20 '20 at 09:12

Use the method RemoveAll, here the doc

Example:

public static void main(String[] args) {
List<Integer> numbersA = new ArrayList<>();
List<Integer> numbersB = new ArrayList<>();
numbersA.addAll(Arrays.asList(new Integer[] { 1, 3, 4, 7, 5, 2 }));
numbersB.addAll(Arrays.asList(new Integer[] { 13, 32, 533, 3, 4, 2 }));
System.out.println("A: " + numbersA);
System.out.println("B: " + numbersB);

numbersB.removeAll(numbersA);
System.out.println("B cleared: " + numbersB);
}

this will print

A: [1, 3, 4, 7, 5, 2]

B: [13, 32, 533, 3, 4, 2]

B cleared: [13, 32, 533]

score 0 · Answer 2 · answered Jul 24 '16 at 15:13

0

You can use boolean removeAll(Collection<?> c); method of List. It will remove the common element.

numbersB.removeAll(numbersA);

answered Jul 24 '16 at 15:13

sauumum

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Alexander Petrov · Answer 3 · 2016-07-24T15:36:01.557

0

 Java 8 version

Version 1 Mutating the original Array

Integer [] array1 = new Integer[]{1,3,4,7,5,2};
Integer [] array2 = new Integer[]{13,32,533,3,4,2};

List<Integer> numbersA=Arrays.asList(array1);
final List<Integer> numbersB=Arrays.asList(array2);

numbersA.stream().forEach(t->numbersB.remove(t));

Version 1 using filter and returning new List

Integer [] array1 = new Integer[]{1,3,4,7,5,2};
    Integer [] array2 = new Integer[]{13,32,533,3,4,2};

    List<Integer> numbersA=Arrays.asList(array1);
    final List<Integer> numbersB=Arrays.asList(array2);

   List<Integer> numbersA.stream().filter(t->numbersB.contains(t)).collect(Collectors.toList());

edited Jul 24 '16 at 15:36

answered Jul 24 '16 at 15:20

Alexander Petrov

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I don't really like your answer, first of all you don't need to create a List from an array to get the stream, and second you're changing state in the forEach when you could use filter and collect to another array, I think it would be much clearer/cleaner – Pedro David Jul 24 '16 at 15:24

How can I remove object in one array from another array?

3 Answers3

Example: