一些字符串相关面试题的java实现

1.字符串右移n位
2.字符串反转
3.返回任意整数对应二进制形式中的1的个数
4.显示字符串中字符的所有排序

import java.util.ArrayList;
import java.util.List;

public class Test4{
	public static void main(String[] args){
		System.out.println(strMoveLeft("alhgon1o4n34lln1231",10));
		System.out.println(strReverse("alhgon1o4n34lln1231b"));
		System.out.println(oneStat(15));
		sort("abcj");
	}
	
	//字符串右移n位
	private static String strMoveLeft(String a,int moveNum){		
		char[] a1 = a.toCharArray();
		char[] b1 = new char[a1.length];
		moveNum %= a.length();	//移动位数可能大于数组长度
		
		for(int i=0;i<a1.length;i++){
			if(i-moveNum>=0){
				b1[i-moveNum] = a1[i];
			}else{
				b1[i-moveNum+a1.length] = a1[i];
			}
		}
		return String.valueOf(b1);
	}
	//字符串反转
	private static String strReverse(String a){
		char[] a1 = a.toCharArray();
		
		for(int i=0;i<a1.length/2;i++){
			char temp = a1[i];
			a1[i] = a1[a1.length-i-1];
			a1[a1.length-i-1] = temp;
		}
		return String.valueOf(a1);
	}
	//返回任意整数对应二进制形式中的1的个数
	private static int oneStat(int i){
		int b = 0;
		while(i>0){
			if(i%2==1){
				b+=1;
			}
			i/=2;
		}
		return b;
	}
	//显示字符串中字符的所有排序，没有去重
	private static void sort(String a){
		char[] a1 = a.toCharArray();
		List<Character> list = new ArrayList<Character>();
		for(int i=0;i<a1.length;i++){
			list.add(a1[i]);
		}
		StringBuffer sb = new StringBuffer();
		display(list, sb);
	}
	
	private static void display(List<Character> list,StringBuffer sb){
		if(list.size()==0){
			System.out.println(sb.toString());
			return;
		}
		for(int i=0;i<list.size();i++){
			List<Character> dealList = new ArrayList<Character>(list);
			StringBuffer dealSb = new StringBuffer(sb);
			
			dealSb.append(String.valueOf(list.get(i)));
			dealList.remove(i);
			
			display(dealList,dealSb);//递归实现
		}
	}
	
}