Java Strings

String methods and concatenation.

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A String is an object holding text. Useful methods:

length(), toUpperCase(), toLowerCase()
indexOf(), contains(), startsWith()
substring(start, end), charAt(i)
replace(), trim(), split()
String.format() and String.join()

Compare strings with a.equals(b), not ==. == checks whether they are the same object.

Key Takeaways: Java Strings

Mastering Java Strings helps you write clean and reliable Java code. Follow standard conventions, test edge cases, and keep logic simple. Try running the code example below and complete the exercises to build confidence.

Java Strings Code Example

Java

public class Main {
    public static void main(String[] args) {
        String s = "  Learn Java at CodesInTech  ".trim();

        System.out.println(s.length());
        System.out.println(s.toUpperCase());
        System.out.println(s.substring(6, 10));
        System.out.println(s.contains("Codes"));
        System.out.println(s.replace("Java", "Kotlin"));
        System.out.println(String.join("-", s.split(" ")));
        System.out.println(String.format("%s has %d chars", "Java", 4));
        System.out.println("java".equals("java"));
    }
}

Output

25
LEARN JAVA AT CODESINTECH
Java
true
Learn Kotlin at CodesInTech
Learn-Java-at-CodesInTech
Java has 4 chars
true

Run this example on your own computer. The "Get Started" lesson shows how to set it up.

Java Strings Practice Exercises

Check what you learned in “Java Strings”.

/ 2 solved

Fill in the blank

Compare two strings by content.

if (a.(b)) { }

✓ Correct! Not quite. Try again.

Multiple choice

Which method returns part of a string?

substring() slice() part() cut()

✓ Correct! Not quite. Try again.

to save your exercise progress.

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Java Strings

💡 Key Takeaways: Java Strings

Java Strings Code Example

Java Strings Practice Exercises

Key Takeaways: Java Strings