Are String Arrays mutable?

问题

I wonder if String arrays in Java are mutable ? I know that Strings are immutable, but how about string Arrays ?

If I have a string array, and change the content, will a new string object be created ? Or will the actual value just be changed ?

Thanks in advance

回答1:

The Strings contained in the String[] are indeed immutable, but the array is mutable.

This is well explained in this answer:

• Immutability means that objects of a certain type can not change in any meaningful way to outside observers
  • Integer, String, etc are immutable
  • Generally all value types should be
• Array objects are mutable
  • It may be an array of references to immutable types, but the array itself is mutable
    • Meaning you can set those references to anything you want
    • Also true for array of primitives
  • An immutable array will not be practical
• References to objects can be shared
  • If the object is mutable, mutation will be seen through all these references

EDIT:

Somewhat related: Why can't strings be mutable in Java and .NET?

回答2:

As far as i remember the field in your array will reference another String

String[] array {"I","like","rain"};
array[2] = "sun"

your array can be changed. the Strings themselves not.

回答3:

In Arrays, each element is just a pointer to an object. So, when you do something like

String one = "1";
String two = "2";
String three = "3";
String four = "4";
String[] myStringArray = {one, two, three};
myStringArray[2] = four;

Then the pointer that was at the 3rd element of the array now points to the four instead of three.

来源：https://stackoverflow.com/questions/16125616/are-string-arrays-mutable