java排列组合算法（n选n）

package xxx.xxx.xxx;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.ArrayList;

import java.util.Random;

import com.wxb.object.Rectangle;

/**

 * @author wxb 2015年11月11日

 */

public class Test04 {
public static void main(String[] args) throws IOException {
ArrayList<Integer> list = new ArrayList<Integer>();
PrintWriter out=new PrintWriter("1_9.txt");

for (int s = 1; s < 10; s++)
list.add(s);
System.out.println(list);

ArrayList<String> result = getResult(list);
int i=0;
for(String s:result){

out.println(s);
System.out.println(s);
if(i%10000==0){
out.flush();
}
i++;
}

out.close();
System.out.println("over...");
}

/**
* @param list
* @return
*/
private static ArrayList<String> getResult(ArrayList<Integer> list) {
// TODO Auto-generated method stub
ArrayList<String> result = new ArrayList<String>();
ArrayList<Integer> next;
if (list.size() == 1){
result.add(list.get(0)+"");
return result;
}
else {
for (int i = 0; i < list.size(); i++) {
next = new ArrayList<Integer>();
for (int j = 0; j < list.size(); j++) {
if (j != i)
next.add(list.get(j));
}
for (String s : getResult(next)) {
result.add(list.get(i)+ s);
}
}
return result;
}
}

}