Java LinkedList contains() method
Syntax and Examples

Introduction

The contains() method in Java's LinkedList class is a handy tool to check if a specific element exists within the list. Think of it like searching for something in a drawer – you want to quickly confirm if what you’re looking for is already there.

Syntax

public boolean contains(Object o)

Parameters

Parameter	Description
o	The object to be checked for equality. It can be any type of object.

Return Value

The contains() method returns a boolean value:

• true: If the list contains the specified element.
• false: If the list does not contain the specified element.

Examples

Example 1: Checking for a String Element

This example demonstrates how to use contains() to see if a specific string is present in a LinkedList of strings.

import java.util.LinkedList;

public class ContainsExample {
    public static void main(String[] args) {
        LinkedList<String> names = new LinkedList<>();
        names.add("Alice");
        names.add("Bob");
        names.add("Charlie");

        String searchName = "Bob";
        boolean containsBob = names.contains(searchName);

        System.out.println("Does the list contain '" + searchName + "'? " + containsBob);
    }
}

Does the list contain 'Bob'? true

Explanation: We create a LinkedList of strings. Then, we use contains() to check if it contains the string "Bob". Since "Bob" is present in the list, the method returns true.

Example 2: Checking for an Integer Element

This example shows how to use contains() with a LinkedList of integers.

import java.util.LinkedList;

public class ContainsIntegerExample {
    public static void main(String[] args) {
        LinkedList<Integer> numbers = new LinkedList<>();
        numbers.add(10);
        numbers.add(20);
        numbers.add(30);

        int searchNumber = 40;
        boolean containsForty = numbers.contains(searchNumber);

        System.out.println("Does the list contain " + searchNumber + '? ' + containsForty); 
    }
}

Does the list contain 40? false

Explanation: We create a LinkedList of integers. We then use contains() to check if it contains the integer 40. Since 40 is not in the list, the method returns false.

Example 3: Checking for an Object with Null

This example demonstrates how the LinkedList handles null values when using the contains() method

import java.util.LinkedList;

public class ContainsNullExample {
    public static void main(String[] args) {
        LinkedList<String> strings = new LinkedList<>();
        strings.add("Hello");
        strings.add(null);
        strings.add("World");

        boolean containsNull = strings.contains(null);

        System.out.println("Does the list contain null? " + containsNull); 
    }
}

Does the list contain null? true

Explanation: A LinkedList can contain null values, and contains(null) will return true if a null value is present in the list.