package cn.edu.bjut.chapter6;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class ArrayListConstructorTester {
	public static String getRandomString(int length) { 
		String base = "abcdefghijklmnopqrstuvwxyz0123456789";
		Random random = new Random();
		StringBuffer sb = new StringBuffer(length);
		for (int i = 0; i < length; i++) {
			int number = random.nextInt(base.length());
			sb.append(base.charAt(number));
		}
		return sb.toString();
	}

	public static void main(String[] args) {
		int n = 1000000;

		long startTime1 = System.currentTimeMillis();
		List<String> list1 = new ArrayList<String>();
		for (int i = 0; i < n; i++) {
			list1.add(getRandomString(5));
		}
		long endTime1 = System.currentTimeMillis();

		long startTime2 = System.currentTimeMillis();
		List<String> list2 = new ArrayList<String>(n);
		for (int i = 0; i < n; i++) {
			list2.add(getRandomString(5));
		}
		long endTime2 = System.currentTimeMillis();

		System.out.println((endTime1 - startTime1) + "ms\t" 
				+ (endTime2 - startTime2) + "ms");
	}
}