Java: 2 lists containing same elements in different order - How to delete same element?

Question

I have this situation:

List<MyClass> list_1 = new ArrayList<>();
List<MyClass> list_2 = new ArrayList<>();
list_1.add(elements...);
list_2.add(same elements...);
mixList(list_1);  //mixing the inner order between the elements
mixList(list_2);
MyClass mClass = list_1.get(5);  //for example place 5 
//TODO: How to remove above element who is exist
//in list_2 also, from list_2?

Note - also it is same elements, but it's not same objects:

//same elements, different objects
MyClass m1 = new MyClass("name", 1);
MyClass m2 = new MyClass("name", 1);

Well if it does, it makes things much, much easier... you can just call `list_2.remove(list_1.get(5))` first... — Jon Skeet, Sep 14 '15 at 18:15

score 1 · Accepted Answer · edited May 23 '17 at 11:51

1

Problem 1 :

//same elements, different objects
MyClass m1 = new MyClass("name", 1);
MyClass m2 = new MyClass("name", 1);

To recognise them, you should implement equals() method.

To start with : How to override equals method in java

Problem 2 :

You can remove same items by writing

list2.removeAll(list1);

note that, you have to implements your equals() method to make it work.

edited May 23 '17 at 11:51

Community

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answered Sep 14 '15 at 18:14

Suresh Atta

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Your `for` loop is entirely equivalent to `list2.removeAll(list1)`. – Louis Wasserman Sep 14 '15 at 18:14

Java: 2 lists containing same elements in different order - How to delete same element?

1 Answers1