JVM-graphics display bytecode execution engine execution process, jvm-bytecode

JVM-graphics display bytecode execution engine execution process, jvm-bytecode

In my previous blog JVM-String comparison-bytecode analysis, I introduced the reasons for String comparison. By analyzing bytecode, this blog will show the internal bytecode execution process of the method.

Not to mention, paste the Java method code we will analyze:

public static void bb(){     String s1="a"+"b";     String s2 = "ab";     p(s1==s2);//true}

Paste the bytecode of the Java method to be analyzed:

Public static void bb (); flags: ACC_PUBLIC, ACC_STATIC Code: stack = 2, locals = 2, args_size = 0
0: ldc #5 // String AB pushes the String "AB" from the constant pool to the top of the stack. 2: astore_0 pushes the reference type of the top stack (String "AB ") store the first local variable 3: ldc #5 // String AB to push the String "AB" from the constant pool to the top 5: astore_1 of the stack (String "AB ") store the first local variable 6: aload_0, push the first local variable ("AB") to the top of the stack 7: aload_1, and then the second local variable ("AB ") push to the top of the stack 8: if_acmpne 15 compare the top two reference type values, the results are different jump (the same here) 11: iconst_1 push int type 1 to the top of the stack 12: goto 16 jump to 16 bytecode offset unconditionally 15: iconst_0 16: invokestatic #10 // Method java/lang/Boolean. valueO calls the static method Boolean. valueOf (); and press true of the returned Boolean type to the top of the stack f :( Z) Ljava/lang/Boolean; 19: invokestatic #11 // Method p :( Ljava/lang/Object;) V calls the static Method p (true); outputs true 22: return returns void from the current Method

From Code: the first line below, we know that the depth of the operand stack is 2, the local variable space is 2 slots, and the number of parameters is 0.

 

If you copy all the images, you will see the results of dynamic execution.

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