java: advantages of immutable objects in examples

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Closed 7 years ago.

give me please examples where I could see advantages of immutable objects. Info I found in internet are concentrated in threads. I don't know about threads yet. would be great if the examples would use simple principles

Answer 1

A good example is the String class:

A good summary of reasons for immutable objects can be found here

Answer 2

As Java returns by value (i.e. object references are returned from methods), if for example I return a String like so:

private String myString = "foo";

public String getString() {
    return this.myString;
}

and the String class wasn't immutable, then the caller of getString() could modify myString, which may not be the desired behaviour; other parts of the system might not want or expect myString to change. So the caller can only change the object which myString points to, not myString itself.