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();}}}