Map、Set、List初始化大小的影响

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class Test
{

    public static void main(String[] args)
    {
	testHashMap(16);
	testHashMap(5000000);
	System.out.println("----------------");
	testHashSet(16);
	testHashSet(5000000);
	System.out.println("----------------");
	testArrayList(16);
	testArrayList(5000000);
    }

    public static void testHashMap(int initSize)
    {
	Map<Integer, String> map = new HashMap<Integer, String>(initSize);

	long beginTime = System.currentTimeMillis();
	for (int i = 0; i < 5000000; i++)
	{
	    map.put(i, "hellooiuytrewq");
	}
	long endTime = System.currentTimeMillis();
	System.out.println(endTime - beginTime);
    }

    public static void testHashSet(int initSize)
    {
	Set<Integer> set = new HashSet<Integer>(initSize);

	long beginTime = System.currentTimeMillis();
	for (int i = 0; i < 5000000; i++)
	{
	    set.add(i);
	}
	long endTime = System.currentTimeMillis();
	System.out.println(endTime - beginTime);
    }

    public static void testArrayList(int initSize)
    {
	List<Integer> list = new ArrayList<Integer>(initSize);

	long beginTime = System.currentTimeMillis();
	for (int i = 0; i < 5000000; i++)
	{
	    list.add(i);
	}
	long endTime = System.currentTimeMillis();
	System.out.println(endTime - beginTime);
    }

}

　　

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2832
2088
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