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java - Java中的二进制和十六进制负数

问题描述

我有这个程序可以打印出任何基数的数字，但我只是想知道如何让它以二进制或十六进制打印负数。该方法被调用printInt，当我尝试以二进制打印负数时它只返回 0，并且它StringIndexOutOfBoundsException为十六进制输入引发异常。这是代码：

import java.util.Scanner;

public class Nums {


    public static final String DIGIT_TABLE = "0123456789abcdef";


    //prints nums in any base
      public static void printInt(long n, int base){
        if(n >= base){
            printInt(n / base, base); 
        }
        System.out.print(DIGIT_TABLE.charAt((int) (n % base)));
      }

      //prints n in decimal form
      /*public static void printDecimal(long n){
        if(n >= 10){
            printDecimal(n / 10);      

        }
        System.out.print((char) ('0' + (n%10)) + " ");
      }*/

      public static void main(String[] args) {

          Scanner s = new Scanner(System.in);
          System.out.println("Enter 5 numbers in the following order: 1 long value to see it in decimal form, a long value and a int for the base "
                + "to be represented in and a long and a base for another number ");
          long input1 = s.nextLong();
          long input2 = s.nextLong();
          int input3 = s.nextInt();
          long in4 = s.nextLong();
          int in5 = s.nextInt();
            System.out.println("Prints number in decimal form");
            //printDecimal(input1);
            System.out.println();
            System.out.println("Prints number in binary: ");
            printInt(input2, input3);
            System.out.println();
            System.out.println("Number in hex");
            printInt(in4, in5);
    }
}

标签： java

解决方案

在您的方法中添加一条if语句printInt来处理负数：

//prints nums in any base
public static void printInt(long n, int base) {
    if (n < 0) {
        System.out.print('-');
        n = -n;
    }
    if (n >= base) {
        printInt(n / base, base); 
    }
    System.out.print(DIGIT_TABLE.charAt((int) (n % base)));
}

此更改的示例会话：

Enter 5 numbers in the following order: 1 long value to see it in decimal form, a long value and a int for the base to be represented in and a long and a base for another number 
-314
-314
2
-314
16
Prints number in decimal form

Prints number in binary: 
-100111010
Number in hex
-13a

极端情况：这不适用于数字 -9 223 372 036 854 775 808，最小长值，因为 along不能保存相应的正值。我认为正确的解决方案是输入验证。例如，要求 long 值在 -1 000 000 000 000 000 000 到 1 000 000 000 000 000 000 范围内，并且碱基在 2 到 16 之间。

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