Check if an ArrayList contains every element from another ArrayList

Question

How do I check if an ArrayList contains all of the objects in another ArrayList? I am looking (if it exists) for something along the lines of:

//INCORRECT EXAMPLE:
if(one.contains(two))
{
    return true;
}
else
{
    return false;
}

For example:

ArrayList one = {1, 2, 3, 4, 5}

ArrayList two = {1, 2, 3} --> True
ArrayList two = {} --> True
ArrayList two = {1, 2, 3, 4, 5} --> True
ArrayList two = {1, 5, 2} --> True
ArrayList two = {1, 7, 4} --> False
ArrayList two = {0, 1, 3} --> False
ArrayList two = {4, 5, 6} --> False
ArrayList two = {7, 8, 9} --> False

And you can reduce your if statement to one line: return one.containsAll(two); — Code-Apprentice
– Code-Apprentice, Commented Jan 25, 2013 at 0:40

C-Otto · Accepted Answer · 2013-01-24 22:41:04Z

137

There is a method called containsAll declared in the java.util.Collection interface. In your setting one.containsAll(two) gives the desired answer.

edited Jan 24, 2013 at 22:41

answered Jan 24, 2013 at 22:07

C-Otto

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Comments

splungebob · Accepted Answer · 2013-01-24 22:07:31Z

16

Per the List interface:

myList.containsAll(...);

answered Jan 24, 2013 at 22:07

splungebob

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Comments

Damian Jeżewski · Accepted Answer · 2013-01-24 22:07:52Z

11

Take a look at containsAll(Collection<?> c) method from List interface. I think it is what you are looking for.

answered Jan 24, 2013 at 22:07

Damian Jeżewski

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Comments

JimiMac · Accepted Answer · 2016-08-12 15:35:06Z

9

Here is another example use of containsAll() that I have used for asserting that two arrays are equal in JUnit testing:

List<String> expected = new ArrayList<String>();
expected.add("this");
expected.add("that");
expected.add("another");

List<String> actual = new ArrayListString();
actual.add("another");
actual.add("that");
actual.add("this");

Assert.assertTrue("The lists do not match!", expected.containsAll(actual));

answered Aug 12, 2016 at 15:35

JimiMac

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Comments

tckmn · Accepted Answer · 2013-01-24 22:07:21Z

5

Your code in the example doesn't make sense, but here's an example anyway.

ArrayList<Integer> one, two;
//initialize
boolean good = true;
for (int i = 0; i < two.size(); i ++) {
    if (!(one.contains(two.get(i))) {
        good = false;
        break;
    }
}

It simply loops through all of two's elements and checks to see if they are in one.

Then the boolean good contains the value you want.

See ArrayList#contains.

EDIT: oh wow, I totally forgot containsAll. Oh well, this is an alternate way to do it if you really want to understand it.

answered Jan 24, 2013 at 22:07

tckmn

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3 Comments

Lee Meador Over a year ago

Once it goes 'false' you should 'break'. No need to keep checking the rest.

Tom Over a year ago

Alternatively (instead of break) you could do: for (int i = 0; i < two.size() && good; i ++)

Lee Meador Over a year ago

If you know that 'one' is ordered from small to large you could do a binary search in real code, but that would only help, timewise, if you expected 'one' to be pretty big.

Sergey Kalinichenko · Accepted Answer · 2013-01-24 22:09:11Z

5

You can use containsAll method of the list to do the check. However, this is a linear operation. If the list is large, you should convert it to HashSet first, and then perform containsAll:

HashSet tmp = new HashSet(one);
if (tmp.containsAll(two)) {
    ...
}

If the length of one is N and the length of two is M, this solution has time complexity of O(M+N); the "plain" containsAll has the complexity of O(M*N), which may be significantly worse.

answered Jan 24, 2013 at 22:09

Sergey Kalinichenko

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Piyush Aggarwal · Accepted Answer · 2021-05-14 11:49:28Z

4

This can also be done using streams in Java

    List<String> employeeList = Arrays.asList("Marc","john");
    List<String> masterEmployeeList = Arrays.asList("Marc", "Stacy", "john");
    System.out.println(employeeList.stream().allMatch(masterEmployeeList::contains));

answered May 14, 2021 at 11:49

Piyush Aggarwal

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NoName NoName · Accepted Answer · 2023-08-25 04:07:56Z

-1

java.util.Collections.indexOfSubList(arrayListIS, arrayListIF)

edited Aug 25, 2023 at 4:07

answered Aug 25, 2023 at 4:06

NoName NoName

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1 Comment

Diego Borba Over a year ago

Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.

Yuces · Accepted Answer · 2020-08-19 07:02:20Z

-2

isEqualCollection() method declared in the org.apache.commons.collections.CollectionUtils gives you the collections are same or not.

if (CollectionUtils.isEqualCollection(collectionA,collectionB)) { do smt... }

answered Aug 19, 2020 at 7:02

Yuces

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