What does immutable mean?

What does immutable mean?

• A. The contents of a String can be changed after creation
• B. The contents of a String cannot be changed once the String is created
• C. Strings can only be changed with reflection
• D. Immutability only applies to numeric types

Answer: (B)

Immutability means once an object is created its value cannot change. With strings, this is why operations that seem to modify a string actually produce a new string rather than altering the original one. For example, taking the uppercase version of a string yields a new string like "HELLO" while the original "hello" remains unchanged. This makes strings predictable and safe to share across different parts of a program. The idea that the contents can be changed after creation describes mutable objects, which is the opposite of immutability. The option about using reflection is unrelated to immutability, and immutability isn’t limited to numeric types—there are immutable strings and other immutable data structures as well.

Immutability means once an object is created its value cannot change. With strings, this is why operations that seem to modify a string actually produce a new string rather than altering the original one. For example, taking the uppercase version of a string yields a new string like "HELLO" while the original "hello" remains unchanged. This makes strings predictable and safe to share across different parts of a program.

The idea that the contents can be changed after creation describes mutable objects, which is the opposite of immutability. The option about using reflection is unrelated to immutability, and immutability isn’t limited to numeric types—there are immutable strings and other immutable data structures as well.