Java Lambda expression - Check if string is empty

Last update on April 28 2025 07:58:27 (UTC/GMT +8 hours)

Check if String is Empty

Write a Java program to implement a lambda expression to check if a given string is empty.

Sample Solution:

Java Code:

// Main.java
import java.util.function.Predicate;

public class Main {
    public static void main(String[] args) {
        // Lambda expression to check if a given string is empty
        Predicate isEmptyString = str -> str.isEmpty();

        // Test cases
        String str1 = ""; // empty string
        String str2 = "Java lambda expression!"; // non-empty string

        // Check if the strings are empty using the lambda expression
		System.out.println("String 1:" + str1);
        System.out.println("String 1 is empty: " + isEmptyString.test(str1));
        System.out.println("\nString 2:" + str2);
		System.out.println("String 2 is empty: " + isEmptyString.test(str2));
    }
}

Sample Output:

String 1:
String 1 is empty: true

String 2:Java lambda expression!
String 2 is empty: false

Explanation:

In the above exercise, we define a Predicate functional interface with a lambda expression to check if a given string is empty. The lambda expression uses the isEmpty() method of the String class to determine if the string is empty.

To check if the strings are empty, we create two test cases, str1 and str2, and use the test() method of the Predicate interface. On the console, the results are displayed.

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to implement a lambda expression that checks if a trimmed string is empty or contains only whitespace.
• Write a Java program to create a lambda that validates a list of strings, returning true only if all are empty.
• Write a Java program to implement a lambda expression that checks if a string is empty and, if so, returns a default message.
• Write a Java program to compose a lambda that verifies a string’s emptiness and logs an error if it is.

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