jvm字节码指令

demo:

public class T1 {
    volatile int n = 0;
    public void add() {
        n++;
    }
}

Compiled from "T1.java"
public class com.shishi.jmm.T1 {
  volatile int n;

  public com.shishi.jmm.T1();
    Code:
       0: aload_0
       1: invokespecial #1                  // Method java/lang/Object."<init>":()V
       4: aload_0
       5: iconst_2
       6: putfield      #2                  // Field n:I
       9: return

  public void add();
    Code:
       0: aload_0
       1: dup
       2: getfield      #2                  // Field n:I
       5: iconst_1
       6: iadd
       7: putfield      #2                  // Field n:I
      10: return

  public static void main(java.lang.String[]);
    Code:
       0: return
}

https://www.cnblogs.com/noteless/p/9556928.html， 参考这个指令集对照，也可去Oracle获取这个指令集对照表

分析add方法：

即： 

从局部变量0中装载引用类型值，压栈，获取值，将int型(1)推送至栈顶，加法指令，设置值，返回