Pointer with java and string variable
This question already has an answer here:
First you are assigning the value "hello" (at some place in memory) to test :
test --------------> "hello"
Then, you are setting myname to the same location in memory.
test --------------> "hello"
/
myname ----------/
Then, you are assigning the value "how are you?" at a new location in memory to test :
-> "hello"
/
myname ----------/
test --------------> "how are you?"
It's all about the pointers.
EDIT AFTER COMMENT
I have no idea what the rest of your code looks like, but if you want to be able to update a single String and have the rest of the references to that String update at the same time, then you need to use a StringBuilder (or StringBuffer if you need synchronization) instead:
StringBuilder test = new StringBuilder("hello");
StringBuilder myname = test;
StringBuilder foo = test;
StringBuilder bar = test;
test.replace(0, test.length(), "how are you?");
Assert.assertEquals("how are you?", test.toString());
Assert.assertEquals("how are you?", myname.toString());
Assert.assertEquals("how are you?", foo.toString());
Assert.assertEquals("how are you?", bar.toString());
Got it from there?
It sounds like you need to learn about the difference between a reference variable and the object that a variable refers to. Let's look at what your code does:
String test = "hello";
This assigns the reference variable test to refer to a constant String object with the value "hello" .
String myname = test;
Now the reference myname refers to the same String object as test does.
test = "how are you ?";
Now test refers to a new String object with the value of "how are you ?" . Note that this does not change myname , as you have seen.
The problem is that String is immutable so "how are you ?" is a new object. Thus myname still refers to the old object "hello" .
Solution 1: Don't use two references. Why not just use test throughout your code if there's only one object?
Solution 2: Have the two references point to the same object, but use a mutable object. eg use StringBuilder or StringBuffer instead of String .
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