JuniorTheoryCommon

What does the program print?

JAVA

public class Main {
    public static void main(String[] args) {
        StringBuilder sb = new StringBuilder("abc");
        sb.append("d").reverse();
        System.out.println(sb);
    }
}

dcba

Expecting abc: unlike a String, a StringBuilder is mutable; append and reverse change sb itself, so no assignment is needed.
Expecting cbad: a chain of calls runs left to right, so append("d") comes first and reverse flips abcd.

Why is StringBuilder preferred over + when a string is built in a loop?
How does StringBuilder differ from StringBuffer?

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Back to questions

JuniorTheoryCommon

What does the program print?

JAVA

public class Main {
    public static void main(String[] args) {
        StringBuilder sb = new StringBuilder("abc");
        sb.append("d").reverse();
        System.out.println(sb);
    }
}

dcba

Expecting abc: unlike a String, a StringBuilder is mutable; append and reverse change sb itself, so no assignment is needed.
Expecting cbad: a chain of calls runs left to right, so append("d") comes first and reverse flips abcd.

Why is StringBuilder preferred over + when a string is built in a loop?
How does StringBuilder differ from StringBuffer?

Back to questions Open topic in roadmap →Answer it yourself — Quiz