Question

I know that String a = “hello”; will put the “hello” into string literal pool. my question is:
1.

String a = "hello";
String b = "hell"+"o";

Does the string literal pool has three object: “hello”, “hell”, and “o”?

2.

String a = "hello";
String b = new String("hello");

then there will be a “hello” object in string literal pool and a string object in heap?

3.

BufferedReader br = new BufferedReader(new FileReader("names"));
String line = br.readLine(); //(the value of line is "hello" now, for example)

then there will be a “hello” object in string literal pool and a string object in heap?

Answer 1

AFAIk, these are the things happening:

1.when javac compiler encounters the above line, it will change it to StringBuffer like this:

String b = new StringBuffer().append("hell").append("o").toString();

String a will be in pool with the value "hello".

2 String b will in the heap.

3.This is purely an in memory operation as it is loading the file contents dynamically.Java compiler never

get a chance to know its memory structure because it is depending on the file size now.So it cannot be pooled.But when you perform a intern() these are the things happening:

If you call a string with method intern(), it is definitely garbage collected in modern JVMS.
It can be used to save memory if many string with the same content.

There is a nice discussion about this here:

Is it good practice to use java.lang.String.intern()?