相關解決：

package com.swordRefersToOffer;

import java.util.Arrays;

/**
 * @author 凌龍
 * @date 2018/9/28
 */

public class Test {
    public static void main(String[] args) {
        Test test = new Test();
//        test.printToMax(1);
        test.printToMax2(2);
    }
    /**
     *方法一：
     */

    /**字串上模擬加法     *      * @param n     */
    public void printToMax(int n){
        if(n < 0)
            return;
        char[] number = new char[n];
        //    初始化       //    for(int i = 0; i < n; i++) number[i] = '0';
        Arrays.fill(number, '0');//字串填充0;
        while(!increment(number)){
            printNumber(number);
        }
        return;
    }

    public boolean increment(char[] num){
        boolean isOverflow = false;
        int size = num.length;
        int carry = 0;
        for(int i = size - 1; i >= 0; i--){
            int temp = num[i] - '0' + carry;
            if(i == size - 1)
                temp++;
            if(temp >= 10){
                if(i == 0) //最高位溢位
                    isOverflow = true;
                else{
                    temp -= 10;
                    carry = 1;
                    num[i] = (char) ('0' + temp);
                }
            }else{
                num[i] = (char)('0' + temp);
                break;
            }
        }
        return isOverflow; }


    public void printNumber(char[] num){
        int size = num.length;
        int i = 0;
        while(i < size && num[i] == '0') //i < size在前，否則越界
            i++;      //char[] printNum = new char[size - i];       //System.arraycopy(num, i, printNum, 0, size - i);//複製陣列
        if(i == size)//不列印全0
            return;
        char[] printNum = Arrays.copyOfRange(num, i, size);//複製陣列
        System.out.println(printNum);
    }

    /**
     *方法二：
     */

    /**字元每一位進行全排列   *      * @param n     */
    public void printToMax2(int n){
        if(n <= 0)
            return;
        char[] number = new char[n];
        Arrays.fill(number, '0');
        printOrder(number,n,0);    }

    public void printOrder(char[] number, int n, int loc){
        if(loc == n) return;
        for(int i = 0; i <= 9; i++){
            number[loc] = (char)('0' + i);
            if(loc == n - 1){
                printNumber(number);
            }
            printOrder(number,n,loc + 1);
        }
    }
}