public class Foo {

    int mSplat;

    static Foo mArray[] = new Foo[27];

 

    public static void zero() {

        int sum = 0;

        for (int i = 0; i < mArray.length; i++) {

            sum += mArray[i].mSplat;

        }

    }

 

    public static void one() {

        int sum = 0;

        Foo[] localArray = mArray;

        int len = localArray.length;

 

        for (int i = 0; i < len; i++) {

            sum += localArray[i].mSplat;

        }

    }

 

    public static void two() {

        int sum = 0;

        for (Foo a: mArray) {

            sum += a.mSplat;

        }

    }

}

 

下面是对三个方法的说明：

 

zero() 获取静态属性两次，每次循环都获取数组长度一次。

 

one() 将所有静态属性引用到本地变量，避免静态成员的查询。

 

two() uses the enhanced for loop syntax introduced in version 1.5 of the Java programming language. The code generated by the compiler takes care of copying the array reference and the array length to local variables, making it a good choice for walking through all elements of an array. It does generate an extra local load/store in the main loop (apparently preserving "a"), making it a teensy bit slower and 4 bytes longer than one().

 

总结：

 

使用增强for循环来处理数组性能是最好的，但必须注意避免附加的对象创建。