String immutability in Java - Practice Problems & Coding Challenges

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Challenge - 5 Problems

💻 code output

intermediate

What is the output of this Java code involving String immutability?

Consider the following Java code snippet. What will be printed when it runs?

Java

public class Test {
    public static void main(String[] args) {
        String s = "hello";
        s.toUpperCase();
        System.out.println(s);
    }
}

A HELLO

B Compilation error

C null

D hello

💻 code output

intermediate

What does this code print after String concatenation?

Look at this Java code. What will be printed?

Java

public class Test {
    public static void main(String[] args) {
        String s = "cat";
        s += "dog";
        System.out.println(s);
    }
}

A dog

B cat

C catdog

D Compilation error

🔧 debug

advanced

Which option causes a compilation error due to String immutability?

Which of the following Java code snippets will cause a compilation error?

A

String s = "hello";
s.charAt(0) = 'H';

B

String s = "hello";
s = s.toUpperCase();

C

String s = "hello";
System.out.println(s.length());

D

String s = "hello";
String t = s + " world";

🧠 conceptual

advanced

How does Java handle String immutability internally?

Which statement best describes how Java implements String immutability?

A Java uses a special String object that allows changes only through reflection.

B Java stores String characters in a final char array that cannot be changed after creation.

C Java copies the String every time it is passed to a method to prevent changes.

D Java uses a mutable char array internally but prevents changes by restricting access.

💻 code output

expert

What is the output of this Java code involving String references?

Analyze the code below. What will be printed?

Java

public class Test {
    public static void main(String[] args) {
        String a = "abc";
        String b = a;
        a = a + "d";
        System.out.println(b);
    }
}

A abc

B abcd

C Compilation error

D null