String STR = new string ("ABC") how many variables are created?

String str = new String(“abc”) Created several variables ?

My answer is 1 A or 2 individual

Why? ？ The process is as follows

1. Look in the constant pool for “abc” object

   • If yes, the corresponding reference instance is returned

   • If not, create the corresponding instance object

2. In the heap new One String(“abc”) object

3. Assign the object address to str4, Create a reference

So the constant pool has "abc" Only one instance object is created , Otherwise, one more object will be created in the constant pool

that String str1 = new String(“A”+“B” ) How many objects will be created ?

I think it's the same as above

Because the compiler will Automatic optimization become

String str1 = new String(“AB”) ;

It can be downloaded from Bytecode From the perspective of

  public static main([Ljava/lang/String;)V
   L0
    LINENUMBER 11 L0
    NEW java/lang/String
    DUP
    LDC "AB"
    INVOKESPECIAL java/lang/String.<init> (Ljava/lang/String;)V
    ASTORE 1
   L1
    LINENUMBER 12 L1
    RETURN
   L2
    LOCALVARIABLE args [Ljava/lang/String; L0 L2 0
    LOCALVARIABLE s Ljava/lang/String; L1 L2 1
    MAXSTACK = 3
    MAXLOCALS = 2
}

ps： Where is the string constant pool ？ Method area ？

jdk1.6 There is a method area . In the method area Runtime constant pool , This period String constant pool In the runtime constant pool , Static variables are also in the method area ..

jdk1.7 Put the string constant pool and static variables To the pile .

jdk1.8 Change the method area to Meta space Separate from the virtual machine memory to the local memory , Dan word String constant pool The pool is still there Pile up in

and Runtime constant pool Moved to Meta space .

Of course , All the above is just a personal summary by reading the articles of other bosses , Welcome to discuss !