Java ArrayList contains() Method

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Description

The Java ArrayList contains(Object) method returns true if this list contains the specified element. The object should have implemented equals() method in order to make this operation successful.

Declaration

Following is the declaration for java.util.ArrayList.contains() method

public boolean contains(Object o)

Parameters

o − The element whose presence in this list is to be tested.

Return Value

This method returns true if this list contains the specified element.

Exception

NA

Example 1

The following example shows the usage of Java ArrayList contains() method. We're using Integers. We'll be adding few elements and then checking if certain element is present or not.

package com.tutorialspoint;
import java.util.ArrayList;
public class ArrayListDemo {
   public static void main(String[] args) {

      // create an empty arrayList
      ArrayList<Integer> arrayList = new ArrayList<>();

      // use add() method to add elements in the arrayList
      arrayList.add(20);
      arrayList.add(30);
      arrayList.add(10);
      arrayList.add(18);        

      // let us print all the elements available in arrayList
      System.out.println("ArrayList = " + arrayList);

      // arrayList contains element 10
      if (arrayList.contains(10)) {
         System.out.println("element 10 is present in the arrayList");
      } else {
         System.out.println("element 10 is not present in the arrayList");
      }

      // arrayList does not contain element 25
      if (arrayList.contains(25)) {
         System.out.println("element 25 is present in the arrayList");
      } else {
         System.out.println("element 25 is not present in the arrayList");    
      }
   }
}           

Output

Let us compile and run the above program, this will produce the following result −

ArrayList = [20, 30, 10, 18]
element 10 is present in the arrayList
element 25 is not present in the arrayList

Example 2

The following example shows the usage of Java ArrayList contains() method with Strings. We'll be adding few elements and then checking if certain element is present or not.

package com.tutorialspoint;
import java.util.ArrayList;
public class ArrayListDemo {
   public static void main(String[] args) {

      // create an empty arrayList
      ArrayList<String> arrayList = new ArrayList<>();

      // use add() method to add elements in the arrayList
      arrayList.add("Welcome");
      arrayList.add("to");
      arrayList.add("tutorialspoint");
      arrayList.add(".com");        

      // let us print all the elements available in arrayList
      System.out.println("ArrayList = " + arrayList);

      // arrayList contains element tutorialspoint
      if (arrayList.contains("tutorialspoint")) {
         System.out.println("element tutorialspoint is present in the arrayList");
      } else {
         System.out.println("element tutorialspoint is not present in the arrayList");
      }

      // arrayList does not contain element html
      if (arrayList.contains("html")) {
         System.out.println("element html is present in the arrayList");
      } else {
         System.out.println("element html is not present in the arrayList");    
      }
   }
}           

Output

Let us compile and run the above program, this will produce the following result −

ArrayList = [Welcome, to, tutorialspoint, .com]
element tutorialspoint is present in the deque
element html is not present in the deque

Example 3

The following example shows the usage of Java ArrayList contains() method with Student objects. We'll be adding few elements and then checking if certain element is present or not.

package com.tutorialspoint;
import java.util.ArrayList;
public class ArrayListDemo {
   public static void main(String[] args) {

      // create an empty arrayList
      ArrayList<Student> arrayList = new ArrayList<>();

      // use add() method to add elements in the arrayList
      arrayList.add(new Student(1, "Julie"));
      arrayList.add(new Student(2, "Robert"));
      arrayList.add(new Student(3, "Adam"));      

      // let us print all the elements available in arrayList
      System.out.println("ArrayList = " + arrayList);

      // arrayList contains element Robert
      if (arrayList.contains(new Student(2, "Robert"))) {
         System.out.println("Student Robert is present in the arrayList");
      } else {
         System.out.println("Student Robert is not present in the arrayList");
      }

      // arrayList does not contain element Jane
      if (arrayList.contains(new Student(4, "Jane"))) {
         System.out.println("Student Jane is present in the arrayList");
      } else {
         System.out.println("Student Jane is not present in the arrayList");    
      }
   }
} 
class Student {
   int rollNo;
   String name;
   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }
   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }   
   @Override
   public boolean equals(Object obj) {
      Student s = (Student)obj;
      return this.rollNo == s.rollNo && this.name.equalsIgnoreCase(s.name);
   }
}

Output

Let us compile and run the above program, this will produce the following result −

ArrayList = [[ 1, Julie ], [ 2, Robert ], [ 3, Adam ]]
Student Robert is present in the deque
Student Jane is not present in the deque