小编给大家分享一下Java如何实现笛卡尔积算法，相信大部分人都还不怎么了解，因此分享这篇文章给大家参考一下，希望大家阅读完这篇文章后大有收获，下面让我们一起去了解一下吧！
具体如下：
笛卡尔积算法的Java实现：
（1）循环内，每次只有一列向下移一个单元格，就是CounterIndex指向的那列。
（2）如果该列到尾部了，则这列index重置为0，而CounterIndex则指向前一列，相当于进位，把前列的index加一。
（3）最后，由生成的行数来控制退出循环。
public class Test { private static String[] aa = { "aa1", "aa2" }; private static String[] bb = { "bb1", "bb2", "bb3" }; private static String[] cc = { "cc1", "cc2", "cc3", "cc4" }; private static String[][] xyz = { aa, bb, cc }; private static int counterIndex = xyz.length - 1; private static int[] counter = { 0, 0, 0 }; public static void main(String[] args) throws Exception { for (int i = 0; i < aa.length * bb.length * cc.length; i++) { System.out.print(aa[counter[0]]); System.out.print("\t"); System.out.print(bb[counter[1]]); System.out.print("\t"); System.out.print(cc[counter[2]]); System.out.println(); handle(); } } public static void handle() { counter[counterIndex]++; if (counter[counterIndex] >= xyz[counterIndex].length) { counter[counterIndex] = 0; counterIndex--; if (counterIndex >= 0) { handle(); } counterIndex = xyz.length - 1; } }}输出共2*3*4=24行：
aa1 bb1 cc1aa1 bb1 cc2aa1 bb1 cc3aa1 bb1 cc4aa1 bb2 cc1aa1 bb2 cc2aa1 bb2 cc3aa1 bb2 cc4aa1 bb3 cc1aa1 bb3 cc2aa1 bb3 cc3aa1 bb3 cc4aa2 bb1 cc1aa2 bb1 cc2aa2 bb1 cc3aa2 bb1 cc4aa2 bb2 cc1aa2 bb2 cc2aa2 bb2 cc3aa2 bb2 cc4aa2 bb3 cc1aa2 bb3 cc2aa2 bb3 cc3aa2 bb3 cc4最近碰到了一个笛卡尔积的算法要求，比如传递过来的参数是"1,3,6,7==4,5,8,9==3,4==43,45,8,9==35,4"，则返回的是一个list，如[1,4,3,43,35][1,4,3,43,4][1,4,3,45,35]……，该list包含是4*4*2*4*2=256个元素，现在的思路是这样的：
import java.util.ArrayList;import java.util.Arrays;import java.util.List;public class DescartesTest { public static void main(String[] args) { // TODO Auto-generated method stub String str ="1,3,6,7==4,5,8,9==3,4==43,45,8,9==35,4"; List<String> result = descartes(str); System.out.println(result); } @SuppressWarnings("rawtypes") public static List<String> descartes(String str) { String[] list = str.split("=="); List<List> strs = new ArrayList<List>(); for(int i=0;i<list.length;i++){ strs.add(Arrays.asList(list[i].split(","))); } System.out.println(strs); int total = 1; for(int i=0;i<strs.size();i++){ total*=strs.get(i).size(); } String[] mysesult = new String[total]; int now = 1; //每个元素每次循环打印个数 int itemLoopNum = 1; //每个元素循环的总次数 int loopPerItem =1; for(int i=0;i<strs.size();i++){ List temp = strs.get(i); now = now*temp.size(); //目标数组的索引值 int index=0; int currentSize = temp.size(); itemLoopNum = total/now; loopPerItem = total/(itemLoopNum*currentSize); int myindex = 0; for(int j=0;j<temp.size();j++){ //每个元素循环的总次数 for(int k=0;k<loopPerItem;k++){ if(myindex==temp.size()) myindex=0; //每个元素每次循环打印个数 for(int m=0;m<itemLoopNum;m++){ mysesult[index]=(mysesult[index]==null?"":mysesult[index]+",")+((String)temp.get(myindex)); index++; } myindex++; } } } return Arrays.asList(mysesult); }}运行结果输出：
[[1, 3, 6, 7], [4, 5, 8, 9], [3, 4], [43, 45, 8, 9], [35, 4]]
[1,4,3,43,35, 1,4,3,43,4, 1,4,3,45,35, 1,4,3,45,4, 1,4,3,8,35, 1,4,3,8,4, 1,4,3,9,35, 1,4,3,9,4, 1,4,4,43,35, 1,4,4,43,4, 1,4,4,45,35, 1,4,4,45,4, 1,4,4,8,35, 1,4,4,8,4, 1,4,4,9,35, 1,4,4,9,4, 1,5,3,43,35, 1,5,3,43,4, 1,5,3,45,35, 1,5,3,45,4, 1,5,3,8,35, 1,5,3,8,4, 1,5,3,9,35, 1,5,3,9,4, 1,5,4,43,35, 1,5,4,43,4, 1,5,4,45,35, 1,5,4,45,4, 1,5,4,8,35, 1,5,4,8,4, 1,5,4,9,35, 1,5,4,9,4, 1,8,3,43,35, 1,8,3,43,4, 1,8,3,45,35, 1,8,3,45,4, 1,8,3,8,35, 1,8,3,8,4, 1,8,3,9,35, 1,8,3,9,4, 1,8,4,43,35, 1,8,4,43,4, 1,8,4,45,35, 1,8,4,45,4, 1,8,4,8,35, 1,8,4,8,4, 1,8,4,9,35, 1,8,4,9,4, 1,9,3,43,35, 1,9,3,43,4, 1,9,3,45,35, 1,9,3,45,4, 1,9,3,8,35, 1,9,3,8,4, 1,9,3,9,35, 1,9,3,9,4, 1,9,4,43,35, 1,9,4,43,4, 1,9,4,45,35, 1,9,4,45,4, 1,9,4,8,35, 1,9,4,8,4, 1,9,4,9,35, 1,9,4,9,4, 3,4,3,43,35, 3,4,3,43,4, 3,4,3,45,35, 3,4,3,45,4, 3,4,3,8,35, 3,4,3,8,4, 3,4,3,9,35, 3,4,3,9,4, 3,4,4,43,35, 3,4,4,43,4, 3,4,4,45,35, 3,4,4,45,4, 3,4,4,8,35, 3,4,4,8,4, 3,4,4,9,35, 3,4,4,9,4, 3,5,3,43,35, 3,5,3,43,4, 3,5,3,45,35, 3,5,3,45,4, 3,5,3,8,35, 3,5,3,8,4, 3,5,3,9,35, 3,5,3,9,4, 3,5,4,43,35, 3,5,4,43,4, 3,5,4,45,35, 3,5,4,45,4, 3,5,4,8,35, 3,5,4,8,4, 3,5,4,9,35, 3,5,4,9,4, 3,8,3,43,35, 3,8,3,43,4, 3,8,3,45,35, 3,8,3,45,4, 3,8,3,8,35, 3,8,3,8,4, 3,8,3,9,35, 3,8,3,9,4, 3,8,4,43,35, 3,8,4,43,4, 3,8,4,45,35, 3,8,4,45,4, 3,8,4,8,35, 3,8,4,8,4, 3,8,4,9,35, 3,8,4,9,4, 3,9,3,43,35, 3,9,3,43,4, 3,9,3,45,35, 3,9,3,45,4, 3,9,3,8,35, 3,9,3,8,4, 3,9,3,9,35, 3,9,3,9,4, 3,9,4,43,35, 3,9,4,43,4, 3,9,4,45,35, 3,9,4,45,4, 3,9,4,8,35, 3,9,4,8,4, 3,9,4,9,35, 3,9,4,9,4, 6,4,3,43,35, 6,4,3,43,4, 6,4,3,45,35, 6,4,3,45,4, 6,4,3,8,35, 6,4,3,8,4, 6,4,3,9,35, 6,4,3,9,4, 6,4,4,43,35, 6,4,4,43,4, 6,4,4,45,35, 6,4,4,45,4, 6,4,4,8,35, 6,4,4,8,4, 6,4,4,9,35, 6,4,4,9,4, 6,5,3,43,35, 6,5,3,43,4, 6,5,3,45,35, 6,5,3,45,4, 6,5,3,8,35, 6,5,3,8,4, 6,5,3,9,35, 6,5,3,9,4, 6,5,4,43,35, 6,5,4,43,4, 6,5,4,45,35, 6,5,4,45,4, 6,5,4,8,35, 6,5,4,8,4, 6,5,4,9,35, 6,5,4,9,4, 6,8,3,43,35, 6,8,3,43,4, 6,8,3,45,35, 6,8,3,45,4, 6,8,3,8,35, 6,8,3,8,4, 6,8,3,9,35, 6,8,3,9,4, 6,8,4,43,35, 6,8,4,43,4, 6,8,4,45,35, 6,8,4,45,4, 6,8,4,8,35, 6,8,4,8,4, 6,8,4,9,35, 6,8,4,9,4, 6,9,3,43,35, 6,9,3,43,4, 6,9,3,45,35, 6,9,3,45,4, 6,9,3,8,35, 6,9,3,8,4, 6,9,3,9,35, 6,9,3,9,4, 6,9,4,43,35, 6,9,4,43,4, 6,9,4,45,35, 6,9,4,45,4, 6,9,4,8,35, 6,9,4,8,4, 6,9,4,9,35, 6,9,4,9,4, 7,4,3,43,35, 7,4,3,43,4, 7,4,3,45,35, 7,4,3,45,4, 7,4,3,8,35, 7,4,3,8,4, 7,4,3,9,35, 7,4,3,9,4, 7,4,4,43,35, 7,4,4,43,4, 7,4,4,45,35, 7,4,4,45,4, 7,4,4,8,35, 7,4,4,8,4, 7,4,4,9,35, 7,4,4,9,4, 7,5,3,43,35, 7,5,3,43,4, 7,5,3,45,35, 7,5,3,45,4, 7,5,3,8,35, 7,5,3,8,4, 7,5,3,9,35, 7,5,3,9,4, 7,5,4,43,35, 7,5,4,43,4, 7,5,4,45,35, 7,5,4,45,4, 7,5,4,8,35, 7,5,4,8,4, 7,5,4,9,35, 7,5,4,9,4, 7,8,3,43,35, 7,8,3,43,4, 7,8,3,45,35, 7,8,3,45,4, 7,8,3,8,35, 7,8,3,8,4, 7,8,3,9,35, 7,8,3,9,4, 7,8,4,43,35, 7,8,4,43,4, 7,8,4,45,35, 7,8,4,45,4, 7,8,4,8,35, 7,8,4,8,4, 7,8,4,9,35, 7,8,4,9,4, 7,9,3,43,35, 7,9,3,43,4, 7,9,3,45,35, 7,9,3,45,4, 7,9,3,8,35, 7,9,3,8,4, 7,9,3,9,35, 7,9,3,9,4, 7,9,4,43,35, 7,9,4,43,4, 7,9,4,45,35, 7,9,4,45,4, 7,9,4,8,35, 7,9,4,8,4, 7,9,4,9,35, 7,9,4,9,4]
递归算法：
public static void fn(List<String[]> list,String[] arr,String str){//迭代list List<String> li = new ArrayList<String>(); for(int i=0;i<list.size();i++){ //取得当前的数组 if(i==list.indexOf(arr)){ //迭代数组 System.out.println(arr.length); for(String st : arr){ st = str + st; if(i<list.size()-1){ fn(list,list.get(i+1),st); }else if(i==list.size()-1){ li.add(st); } } } } for(int i = 0 ; i < li.size();i++ ) { System.out.println(li.get(i)); }}以上是“Java如何实现笛卡尔积算法”这篇文章的所有内容，感谢各位的阅读！相信大家都有了一定的了解，希望分享的内容对大家有所帮助，如果还想学习更多知识，欢迎关注编程网行业资讯频道！
