先把输入的进制，转换成10进制，再用10进制转换到目标进制

import java.util.Scanner;public class Quanneng {public static void main(String[] args) {// TODO Auto-generated method stubScanner input = new Scanner(System.in);System.out.println("****************<<在线进制转换>>*****************");Stack1 s = new Stack1(100);while(true){System.out.println("1,进行计算");System.out.println("2,退出系统");System.out.print("请输入你的选择:");int choices = input.nextInt();if(choices == 1){System.out.print("请输入要输入数字的进制:");int jin = input.nextInt();System.out.print("请输入数据: ");String str = input.next();int result = choice(str,jin);System.out.print("请输入要转为的进制:");int zhuan = input.nextInt();while(result != 0){int temp = result % zhuan;s.push(temp);result /= zhuan;}System.out.print("结果为: ");while(!s.isEmpty()){int temp = s.pop();if(temp >= 0 && temp <= 9){System.out.print(" " + (char)(temp + '0'));}else{System.out.print(" " + (char)(temp - 10 + 'A'));}}System.out.println();}else{System.out.println("退出系统");System.exit(0);}}}//转换成10进制public static int choice(String temp,int jin){int sum = 0;int top = 0;for(int i = temp.length() - 1;i >= 0;i --){char ch = temp.charAt(i);if(ch >= '0' && ch <= '9'){sum += Math.pow(jin,top) * (ch - '0');top ++;}else{sum += Math.pow(jin,top) * (ch - '7');top ++;}}return sum;}}//栈
class Stack1{private int maxsize;private int num[];private int top = -1;public Stack1(int maxsize){this.maxsize = maxsize;num = new int[maxsize];//为栈申请空间}//判断栈是否为满public boolean isFull(){return top == maxsize - 1;}//是否为空public boolean isEmpty(){return top == -1;}//入栈public void push(int temp){if(isFull()){System.out.println("战已满");return;}num[++top] = temp;}//出栈public int pop(){if(isEmpty()){System.out.println("栈已经为空");return -1;}return num[top --];}}