Java Vector contains() Method

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Description

The Java Vector contains(Object elem) method is used to test the existence of an element in a vector.

Declaration

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

public boolean contains(Object elem)

Parameters

elem − This is an object as input.

Return Value

true − It returns true if and only if the specified object is the same as a component in this vector.Otherwise it returns false.

Exception

• ClassCastException − if the type of the specified element is incompatible with this collection (optional).

• NullPointerException − if the specified element is null and this collection does not support null elements (optional).

Checking an Element's Presence in a Vector of Integer Example

The following example shows the usage of Java Vector 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.Vector;

public class VectorDemo {
   public static void main(String[] args) {

      // create an empty vector
      Vector<Integer> vector = new Vector<>();

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

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

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

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

Output

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

Vector = [20, 30, 10, 18]
element 10 is present in the vector
element 25 is not present in the vector

Checking an Element's Presence in a Vector of String Example

The following example shows the usage of Java Vector 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.Vector;

public class VectorDemo {
   public static void main(String[] args) {

      // create an empty vector
      Vector<String> vector = new Vector<>();

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

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

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

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

Output

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

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

Checking an Element's Presence in a Vector of Object Example

The following example shows the usage of Java Vector 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.Vector;

public class VectorDemo {
   public static void main(String[] args) {

      // create an empty vector
      Vector<Student> vector = new Vector<>();

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

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

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

      // vector does not contain element Jane
      if (vector.contains(new Student(4, "Jane"))) {
         System.out.println("Student Jane is present in the vector");
      } else {
         System.out.println("Student Jane is not present in the vector");    
      }
   }
} 
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 −

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