How to Use startsWith and endsWith Methods in Java

In Java, use startsWith(String prefix) to check if a string begins with a specific prefix, and endsWith(String suffix) to check if it ends with a specific suffix. Both methods return a boolean value indicating true or false.

Syntax

The startsWith and endsWith methods belong to the String class in Java. They check if a string starts or ends with a given substring.

• boolean startsWith(String prefix): Returns true if the string starts with prefix.
• boolean endsWith(String suffix): Returns true if the string ends with suffix.

java

String text = "Hello World";
boolean starts = text.startsWith("Hello");
boolean ends = text.endsWith("World");

Example

This example shows how to use startsWith and endsWith to check parts of a string and print the results.

java

public class Main {
    public static void main(String[] args) {
        String message = "Welcome to Java programming!";

        boolean starts = message.startsWith("Welcome");
        boolean ends = message.endsWith("programming!");

        System.out.println("Starts with 'Welcome': " + starts);
        System.out.println("Ends with 'programming!': " + ends);

        // Checking with wrong case
        System.out.println("Starts with 'welcome': " + message.startsWith("welcome"));
    }
}

Output

Starts with 'Welcome': true
Ends with 'programming!': true
Starts with 'welcome': false

Common Pitfalls

Common mistakes include:

• Case sensitivity: startsWith and endsWith are case sensitive, so "Hello" is different from "hello".
• Null strings: Calling these methods on a null string causes NullPointerException.
• Empty strings: Checking with an empty string always returns true because every string starts and ends with an empty string.

java

public class PitfallExample {
    public static void main(String[] args) {
        String text = "Java";

        // Wrong: case sensitive check
        System.out.println(text.startsWith("java")); // false

        // Right: convert to lower case first
        System.out.println(text.toLowerCase().startsWith("java")); // true

        // Empty string check
        System.out.println(text.startsWith("") + " (always true)");

        // Null string example (uncomment to see error)
        // String nullStr = null;
        // System.out.println(nullStr.startsWith("J")); // Throws NullPointerException
    }
}

Output

false
true
true (always true)

Quick Reference

Method	Description	Returns
startsWith(String prefix)	Checks if string starts with prefix	boolean (true/false)
endsWith(String suffix)	Checks if string ends with suffix	boolean (true/false)

Key Takeaways

Use startsWith() to check if a string begins with a specific substring.

Use endsWith() to check if a string ends with a specific substring.

Both methods are case sensitive and return boolean values.

Calling these methods on null strings causes errors.

Empty string as argument always returns true.