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What is the ArrayList.containsAll() method in Java?

Syed Muhammad Ali Mustafa

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

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The ArrayList.containsAll() method in Java is used to check if the list contains all the elements present in a collection.

Syntax

The ArrayList.containsAll() method in Java can be declared as shown in the code snippet below:

boolean containsAll(Collection c)
  • c: The collection whose elements will be checked if they are present in the list.

Return value

The ArrayList.containsAll() method returns a boolean, such that:

  • The return value is true if the list contains all the elements present in the collection c.
  • The return value is false if the list does not contain all the elements present in the collection c.

Note: If the collection is null, the ArrayList.containsAll() method throws the NullPointerException.

Examples

Example 1

Consider the code snippet below, which demonstrates the use of the ArrayList.containsAll() method.

import java.util.*;
public class Example1 {
public static void main(String args[])
{
List<String> list1 = new ArrayList<String>();
list1.add("Hello");
list1.add("world");
list1.add("!");
System.out.println("list1: " + list1);
List<String> list2 = new ArrayList<String>();
list2.add("Hello");
list2.add("world2");
System.out.println("list2: " + list2);
System.out.println("list1.containsAll(): " + list1.containsAll(list2));
}
}

Explanation

Two lists, list1 and list2, are declared in line 7 and line 13 respectively. The ArrayList.containsAll() method is used in line 18 to check if all the elements of list2 are present in list1. The ArrayList.containsAll() method returns false, which means that list1 does not contain all the elements in list2.

Example 2

Consider another example of the ArrayList.containsAll() method.

import java.util.*;
public class Example2 {
public static void main(String args[])
{
List<String> list1 = new ArrayList<String>();
list1.add("Hello");
list1.add("world");
list1.add("!");
System.out.println("list1: " + list1);
List<String> list2 = new ArrayList<String>();
list2.add("Hello");
list2.add("world");
System.out.println("list2: " + list2);
System.out.println("list1.containsAll(): " + list1.containsAll(list2));
}
}

Explanation

Two lists, list1 and list2, are declared in line 7 and line 13 respectively. The ArrayList.containsAll() method is used in line 18 to check if all the elements of list2 are present in list1. The ArrayList.containsAll() method returns true, which means that list1 contains all the elements in list2.

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CONTRIBUTOR

Syed Muhammad Ali Mustafa

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

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