Final principle

Set up final The principle of variable

I understand volatile principle , Another comparison final The implementation of is relatively simple

public class TestFinal {
    
 final int a = 20; 
 }

Bytecode

0: aload_0
1: invokespecial #1 // Method java/lang/Object."<init>":()V
4: aload_0
5: bipush 20
7: putfield #2 // Field a:I
 <--  Write barriers 
10: return

Find out final The assignment of variables will also pass putfield Order to complete , Similarly, a write barrier will be added after this instruction , Ensure that when other threads read its value, it will not appear as 0 The situation of

obtain final The principle of variable

No use final ( lower than short)

Use final( lower than short)

Add final Use constant pools ( higher than short)

No addition final Use constant pools ( higher than short)