Hi guys, I have copied the ArrayList source code from java.util package to my own package. But I found it running solwer than original java.util.ArrayList. 

Test code:

```
@Test
public void jdkApiPerformance() {
    long startTime = System.nanoTime();
    java.util.ArrayList<Object> list = new java.util.ArrayList<Object>();
    long costTime = System.nanoTime() - startTime;
    System.out.println("jdkPerformance cost " + costTime + "ns.");
}

@Test
public void myApiPerformance() {
    long startTime = System.nanoTime();
    question.jdk.ArrayList<Object> list = new question.jdk.ArrayList<Object>();
    long costTime = System.nanoTime() - startTime;
    System.out.println("apiPerformance cost " + costTime + "ns.");
}

```

The outputs for this test as blow:

```

jdkPerformance cost 10263ns.
apiPerformance cost 1244158ns.

```

Obviously, my api runs slower than JDK api. 

Then I added a @Before method for this test:

```
@Before
public void setUp() {
    new java.util.ArrayList<Object>();
    new question.jdk.ArrayList<Object>();
}

```

The outputs for this case are changed:

```

jdkPerformance cost 9932ns.
apiPerformance cost 1324ns.

```

My api runs faster than JDK api!!?

I am really confused for this circumstance.Pls help me.Thanks.