java中arraylist和一维数组,二维数组的转换

package com.xunfang.epay.util;

import java.util.ArrayList;

public class TwoArray {
// 数组转换问题

public static void main(String[] args) {
String str[][] = { { "a1", "a2", "a3" }, { "b1", "b2" },
{ "c1", "c2", "c3", "c4" } };

String arr1[] = { "a1", "a2", "a3" };
String arr2[] = { "b1", "b2" };
String arr3[] = { "c1", "c2", "c3", "c4" };
String strTwo[][] = new String[3][];
String strone1[];

ArrayList<String> list1, list2, list3;
list1 = new ArrayList<String>();
list1.add("a1");
list1.add("a2");
list1.add("a3");

list2 = new ArrayList<String>();
list2.add("b1");
list2.add("b2");

list3 = new ArrayList<String>();
list3.add("c1");
list3.add("c2");
list3.add("c3");
list3.add("c4");

ArrayList<ArrayList<String>> listTwo = new ArrayList<ArrayList<String>>();
listTwo.add(list1);
listTwo.add(list2);
listTwo.add(list3);

// 转成一维数组
strone1 = list1.toArray(new String[list1.size()]);
String strone2[] = list2.toArray(new String[list2.size()]);
String strone3[] = list3.toArray(new String[list3.size()]);

// printOne(strone1);

// 转成二维数组
strTwo[0] = strone1;
strTwo[1] = strone2;
strTwo[2] = strone3;
printTwo(strTwo);
}

private static void printOne(String arr[]) {
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i] + ",");
}
}

private static void printTwo(String arr[][]) {
for (int i = 0; i < arr.length; i++) {
for (int j = 0; j < arr[i].length; j++) {
System.out.print(arr[i][j] + ",");
}
System.out.println();
}
}
}