Java String contains() Method: Check if String contains Substring

Java String contains() method

The Java String contains() method is used to check whether the specific set of characters are part of the given string or not. It returns a boolean value true if the specified characters are substring of a given string and returns false otherwise. It can be directly used inside the if statement.

Syntax of contains() method in Java

public boolean String.contains(CharSequence s)

Parameters

s − This is the sequence to search in Java contains() method

Return Value

The contains() method in Java returns true only if this string contains “s” else false.

Exception

NullPointerException − if the value of s is null in the Java contains() method.

Java String contains() Method Example 1:

public class Sample_String {
    public static void main(String[] args) {
        String str_Sample = "This is a String contains Example";
        //Check if String contains a sequence
        System.out.println("Contains sequence 'ing': " + str_Sample.contains("ing"));
        System.out.println("Contains sequence 'Example': " + str_Sample.contains("Example"));
        //String contains method is case sensitive  
        System.out.println("Contains sequence 'example': " + str_Sample.contains("example"));
        System.out.println("Contains sequence 'is String': " + str_Sample.contains("is String"));
    }
}

Output:

Contains sequence ‘ing’: true
Contains sequence ‘Example’: true
Contains sequence ‘example’: false
Contains sequence ‘is String’: false

When to use Contains() method?

contains() in Java is a common case in programming when you want to check if specific String contains a particular substring. For example, If you want to test if the String “The big red fox” contains the substring “red.” The string contains() in Java method is useful in such situation.

Java String contains() Method Example 2:
Java String contains() method in the if else Structure:

public class IfExample {
    public static void main(String args[]) {
        String str1 = "Java string contains If else Example";
        // In If-else statements you can use the contains() method

        if (str1.contains("example")) {
            System.out.println("The Keyword :example: is found in given string");
        } else {
            System.out.println("The Keyword :example: is not found in the string");
        }
    }
}

Output:

The Keyword :example: is not found in the string class Java

Java String contains() Method: Check if String contains Substring