用Java创建对象很慢

尝试看看您从中得到了什么-进行一些练习以尝试使VM无法优化循环：

import java.util.ArrayList;import java.util.Random;class DummyInteger {    private int i;    public DummyInteger(int i) {        this.i = i;    }    public int getI() {        return i;    }}public class ObjectCreationTest {    final static int ITERATIONS = 2000000;    public static void main(String[] args) {        Random r = new Random(System.currentTimeMillis());        int[] randArr = new int[ITERATIONS];        for(int i = 0; i < ITERATIONS; i++) { randArr[i] = r.nextInt();        }        DummyInteger[] iArr = new DummyInteger[ITERATIONS];        long start = System.currentTimeMillis();        for(int i = 0; i < ITERATIONS; i++) { ArrayList<DummyInteger> list = new ArrayList<DummyInteger>();  list.add(new DummyInteger(randArr[i])); iArr[i] = list.get(0);        }        long end = System.currentTimeMillis();        System.out.println(String.format("Creating %d objects took %d ms",ITERATIONS*2,end-start));        int sum = 0;        for(DummyInteger mi: iArr) { sum += mi.getI();        }        System.out.println(sum);        }}

我有

创建4000000个对象耗时678毫秒

每个对象大约为170纳秒。