Java操作符——i++ 和 ++i的区别

问题：前置自增和后置自增的区别

Code-后置自增

public class Test {
    public static void main(String[] args) {
        int a = 2;
        int b = a++ + a * 3;
        System.out.println(b);
    }
}

Code-前置自增

public class Test2 {
    public static void main(String[] args) {
        int a = 2;
        int b = ++a + a * 3;
        System.out.println(b);
    }
}

 

1.运算过程分析

1.1.后置自增

字节码

public static void main(java.lang.String[]);
  Code:
     0: iconst_2
     1: istore_1
     2: iload_1
     3: iinc          1, 1
     6: iload_1
     7: iconst_3
     8: imul
     9: iadd
    10: istore_2
    11: getstatic     #2      // Field java/lang/System.out:Ljava/io/PrintStream;
    14: iload_2
    15: invokevirtual #3      // Method java/io/PrintStream.println:(I)V
    18: return

字节码分析

 

1.2.前置自增

字节码

public static void main(java.lang.String[]);
  Code:
     0: iconst_2
     1: istore_1
     2: iinc          1, 1
     5: iload_1
     6: iload_1
     7: iconst_3
     8: imul
     9: iadd
    10: istore_2
    11: getstatic     #2      // Field java/lang/System.out:Ljava/io/PrintStream;
    14: iload_2
    15: invokevirtual #3      // Method java/io/PrintStream.println:(I)V
    18: return

字节码分析