Strings in Java — Revision Notes

Definition

Syntax

String name = "text";
name.length();
name.toUpperCase();
name.equals(other);

Example

public class Main {
    public static void main(String[] args) {
        String name = "CodeyHub";
        System.out.println("Name: " + name);
        System.out.println("Length: " + name.length());
        System.out.println("Upper: " + name.toUpperCase());
    }
}

Output

Important Points

• Java String objects are immutable — methods return new strings rather than modifying in place.
• Use .equals(), not ==, to compare string content.
• StringBuilder is the efficient choice for building strings in a loop, since it's mutable.
• Common methods: .length(), .substring(), .indexOf(), .split().

Common Mistakes

• Comparing strings with == instead of .equals().
• Concatenating strings with + repeatedly inside a large loop instead of using StringBuilder.
• Forgetting that string methods don't change the original string — you must capture the returned value.

Interview Tip