Java Storage Location Classic example

String a= "a";
String b= "B";
String c= "AB";
String d= "AB";
String e=a+b;

The memory used to store the data in the program is divided into four blocks
1. Global zone (static zone)
2, text constant area: the constant string is placed in this area, that is, we often talk about the constant pool.
3. Stack: The parameter value of the stored function, the value of the local variable, etc.
4. Heap area (heap): storage Object

When we define a string
String a = "a";
A in the stack area, "a" is a string constant in the constant pool
String B = "B";
b in the stack area, "B" in the constant pool
String c= "AB";
C in the stack area, "AB" in the constant pool
String d= "AB";
D in the stack area, this time the constant pool has "AB", so directly using the already have the "AB"
So the same "AB" in the constant pool that C and D are pointing at this time
String e=a+b;
E in the stack area, A+b actually produces a new string object, since it is a string object, so the result "AB" is placed in the heap area, that e points to the "AB" in the heap
In this case, the C==d is true,c==e to False
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Also, if you define a string object
String str1 = new String ("AB");
STR1 in the Stack area, create the "AB" string object in the heap area
String str2 = new String ("AB");
STR2 is in the stack, and a new "AB" object is also created in the heap area, but not the same as the "AB" just now.
The equivalent of two string objects in the heap area, but the content is just "AB".

So STR1==STR2 is false.

A constant string inside a constant pool can be reused, but it must be the string you use directly, like A +
b This form Although the result is "AB", but not the use of the string constant "AB"

Transferred from: http://blog.sina.com.cn/s/blog_4b622a8e0100c296.html

Java Storage Location Classic example