list复制时，需要首先保证目标list空间足够大，并非指size大小，而是实际容纳大小。

package com.bluejie.bluej.java.base.container;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collections;

import java.util.List;

public class ListCopyDemo {

private static ListCopyDemolistCopyDemo =new ListCopyDemo();

public static void main(String[] args) {

listCopyDemo.copy();

}

private void copy(){

List from =new ArrayList();

from.add("1");

from.add("2");

from.add("3");

//size大小于实际存储数量不同

List to  =new ArrayList(Arrays.asList(new Object[from.size()]));

Collections.copy(to,from);

System.out.println(to.size());

}

}