原始数组的现代 for 循环

Is there any performance difference between the for loops on a primitive array?

假设:

double[] doubleArray = new double[300000];


for (double var: doubleArray) 
   someComplexCalculation(var);

或:

for ( int i = 0, y = doubleArray.length; i < y; i++)
   someComplexCalculation(doubleArray[i]);

测试结果

我实际上分析了它:

Total timeused for modern loop= 13269ms
Total timeused for old loop   = 15370ms

所以现代循环实际上运行得更快，至少在我的 Mac OSX JVM 1.5 上是这样.

1: double[] tmp = doubleArray;
2: for (int i = 0, y = tmp.length; i < y; i++) {
3:   double var = tmp[i];
4:   someComplexCalculation(var);
5: }