Java String Compiler

Strings are immutable in Java. Test your understanding with these snippets — palindrome checks, StringBuilder loops, splits, and more — all runnable in the browser.

Run Java String Compiler examples in the Java compiler

Examples included

Run the string length example
Run the string reverse example
Run the palindrome example
Run the count vowels example
Run the string split example
Run the string builder example
Run the anagram check example

Practical tips

Use s.equals(t) for content comparison. == compares references and gives false positives via string interning.
StringBuilder for any concatenation in a loop. String "+" in a loop is O(N²).
String.chars() gives an IntStream of code points — useful for functional transforms.

Common questions

How do I reverse a string in Java?

Use new StringBuilder(s).reverse().toString(). The example above is editable and runnable.

Why is == wrong for strings?

It checks reference equality. Two strings with the same content can be different objects. Always use .equals().