Must-do problems: Strings

150 min · Beginner

These are the String problems every Java learner should be able to solve. Work them in order from easy to hard, check your program against every test, and open a hint only when you are stuck.

What you will learn

Walk through a String with charAt() and build results with StringBuilder
Use char arithmetic and int[26] counting for letters
Combine split(), substring(), indexOf() and equals() to solve real tasks
Handle edge cases: extra spaces, empty results, ties and very long inputs

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