java - 比较一个简单循环的 java 字节码？

Question

我试图找出这两个循环在编译时的相似程度:

for (int i = 0; i < result.length; i++){
   result[i] = array[((i < index) ? i : i + 1)];
}

和

for (int i = 0; i < result.length; i++){
   if(i < index) result[i] = array[i];
   else result[i] = array[i + 1];
}

我发现很难找出每个循环的操作位置。
我应该如何比较这两个循环？谢谢

这是我使用 javap -c 运行程序时得到的结果:

Compiled from "Test.java"
public class Test {
  public Test();
    Code:
       0: aload_0       
       1: invokespecial #1                  // Method java/lang/Object."<init>":()V
       4: return        

  public static void main(java.lang.String[]);
    Code:
       0: new           #2                  // class Test
       3: dup           
       4: invokespecial #3                  // Method "<init>":()V
       7: pop           
       8: return        

  public void Test();
    Code:
       0: bipush        10
       2: newarray       int
       4: astore_1      
       5: iconst_0      
       6: istore_2      
       7: iload_2       
       8: bipush        10
      10: if_icmpge     23
      13: aload_1       
      14: iload_2       
      15: iload_2       
      16: iastore       
      17: iinc          2, 1
      20: goto          7
      23: aload_0       
      24: aload_1       
      25: iconst_5      
      26: invokespecial #4                  // Method removeAndTrimConcise:([II)[I
      29: pop           
      30: bipush        10
      32: newarray       int
      34: astore_1      
      35: iconst_0      
      36: istore_2      
      37: iload_2       
      38: bipush        10
      40: if_icmpge     53
      43: aload_1       
      44: iload_2       
      45: iload_2       
      46: iastore       
      47: iinc          2, 1
      50: goto          37
      53: aload_0       
      54: aload_1       
      55: iconst_5      
      56: invokespecial #5                  // Method removeAndTrim:([II)[I
      59: pop           
      60: return        
}

Answer 1

应该大致介于 newarray(我假设您在每个循环之前创建一个新数组)和 goto(如您所见，将控制流带回到上一行，因此循环):

第一个循环:

   2: newarray       int
   4: astore_1      
   5: iconst_0      
   6: istore_2      
   7: iload_2       
   8: bipush        10
  10: if_icmpge     23
  13: aload_1       
  14: iload_2       
  15: iload_2       
  16: iastore       
  17: iinc          2, 1
  20: goto          7

第二个:

  32: newarray       int
  34: astore_1      
  35: iconst_0      
  36: istore_2      
  37: iload_2       
  38: bipush        10
  40: if_icmpge     53
  43: aload_1       
  44: iload_2       
  45: iload_2       
  46: iastore       
  47: iinc          2, 1
  50: goto          37

它们看起来非常相似。