十六进制转二进制和十进制转换器

huangapple
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标题翻译

Hexadecimal to binary and decimal converter

问题

public static int hex2decimal(String s) {
    String digits = "0123456789ABCDEF";
    s = s.toUpperCase();
    int val = 0;
    for (int i = 0; i < s.length(); i++) {
        char c = s.charAt(i);
        int d = digits.indexOf(c);
        val = 16 * val + d;
    }
    return val;
}

public static void main(String args[]) {
    String hexdecnum;
    int decnum, i = 1, j;

    int binnum[] = new int[100];
    Scanner scan = new Scanner(System.in);

    System.out.print("Enter Hexadecimal Number : ");
    hexdecnum = scan.nextLine();
    final int MAX_LENGTH = 2;

    if (String.valueOf(hexdecnum).length() <= MAX_LENGTH) {
        /* first convert the hexadecimal to decimal */

        decnum = hex2decimal(hexdecnum);
        System.out.print("Equivalent Dec Number is : " + decnum);
        System.out.println();

        /* now convert the decimal to binary */

        while (decnum != 0) {
            binnum[i++] = decnum % 2;
            decnum = decnum / 2;
        }

        System.out.print("Equivalent Binary Number is : ");
        for (j = i - 1; j > 0; j--) {
            System.out.print(binnum[j]);
        }
    } else {
        System.out.println("ERROR: Invalid Input");
        System.out.print("Enter a number: ");
    }
}
英文翻译

everyone. Here I have a hexa to binary and decimal converter. The problem is when I enter an invalid input such as the letter G or X it gives me a negative output. How can I prevent it from doing this and instead print out that the it is an invalid number

public static int hex2decimal(String s)
	    {
	             String digits = &quot;0123456789ABCDEF&quot;;
	             s = s.toUpperCase();
	             int val = 0;
	             for (int i = 0; i &lt; s.length(); i++)
	             {
	                 char c = s.charAt(i);
	                 int d = digits.indexOf(c);
	                 val = 16*val + d;
	             }
	             return val;
	    }
	
		 public static void main(String args[])
		    {
		        String hexdecnum;
		        int decnum, i=1, j;
		     
		        int binnum[] = new int[100];
		        Scanner scan = new Scanner(System.in);
				
		        System.out.print(&quot;Enter Hexadecimal Number : &quot;);
		        hexdecnum = scan.nextLine();
		        final int MAX_LENGTH = 2;
		          
		              if(String.valueOf(hexdecnum).length() &lt;= MAX_LENGTH) {
		            	  /* first convert the hexadecimal to decimal */
		  		        
		  		        decnum = hex2decimal(hexdecnum);
		  		        System.out.print(&quot;Equivalent Dec Number is : &quot;+ decnum);
		  		        System.out.println();
		  		        
		  		        /* now convert the decimal to binary */
		  		        
		  		        while(decnum != 0)
		  		        {
		  		            binnum[i++] = decnum%2;
		  		            decnum = decnum/2;
		  		        }
		  				
		  		        System.out.print(&quot;Equivalent Binary Number is : &quot;);
		  		        for(j=i-1; j&gt;0; j--)
		  		        {
		  		            System.out.print(binnum[j]);
		  		        }
		              } else {
		                System.out.println(&quot;ERROR: Invalid Input&quot;);
		                System.out.print(&quot;Enter a number: &quot;);
		              }
		            } 
    	

</details>


# 答案1
**得分**: 1

尝试这段代码。你只需要检查 `charAt` 是否返回一个正值，如果返回 -1，意味着你要查找的字符不在该字符串中。

```java
public static int hex2decimal(String s)
{
    String digits = "0123456789ABCDEF";
    s = s.toUpperCase();
    int val = 0;
    for (int i = 0; i < s.length(); i++)
    {
        char c = s.charAt(i);
        int d = digits.indexOf(c);
        if (d != -1)
            val = 16 * val + d;
        else
            return d;
    }
    return val;
}

public static void main(String args[])
{
    String hexdecnum;
    int decnum, i = 1, j;

    int binnum[] = new int[100];
    Scanner scan = new Scanner(System.in);

    System.out.print("Enter Hexadecimal Number : ");
    hexdecnum = scan.nextLine();
    final int MAX_LENGTH = 2;

    if (String.valueOf(hexdecnum).length() <= MAX_LENGTH) {
        /* 首先将十六进制转换为十进制 */

        decnum = hex2decimal(hexdecnum);
        if (decnum == -1)
            System.out.println("Incorrect Hex Value");
        else {
            System.out.print("Equivalent Dec Number is : " + decnum);
            System.out.println();

            /* 现在将十进制转换为二进制 */

            while (decnum != 0) {
                binnum[i++] = decnum % 2;
                decnum = decnum / 2;
            }

            System.out.print("Equivalent Binary Number is : ");
            for (j = i - 1; j > 0; j--) {
                System.out.print(binnum[j]);
            }
        }
    } else {
        System.out.println("ERROR: Invalid Input");
        System.out.print("Enter a number: ");
    }
}
英文翻译

Try this code. You just need to check if the charAt returns a positive value if it returns -1 that means the character you are looking for is not in that string.


    public static int hex2decimal(String s)
    {
        String digits = &quot;0123456789ABCDEF&quot;;
        s = s.toUpperCase();
        int val = 0;
        for (int i = 0; i &lt; s.length(); i++)
        {
            char c = s.charAt(i);
            int d = digits.indexOf(c);
            if (d!=-1)
                val = 16*val + d;
            else
                return d;
        }
        return val;
    }

    public static void main(String args[])
    {
        String hexdecnum;
        int decnum, i=1, j;

        int binnum[] = new int[100];
        Scanner scan = new Scanner(System.in);

        System.out.print(&quot;Enter Hexadecimal Number : &quot;);
        hexdecnum = scan.nextLine();
        final int MAX_LENGTH = 2;

        if(String.valueOf(hexdecnum).length() &lt;= MAX_LENGTH) {
            /* first convert the hexadecimal to decimal */

            decnum = hex2decimal(hexdecnum);
            if (decnum==-1)
                System.out.println(&quot;Incorrect Hex Value&quot;);
            else {
                System.out.print(&quot;Equivalent Dec Number is : &quot; + decnum);
                System.out.println();

                /* now convert the decimal to binary */

                while (decnum != 0) {
                    binnum[i++] = decnum % 2;
                    decnum = decnum / 2;
                }

                System.out.print(&quot;Equivalent Binary Number is : &quot;);
                for (j = i - 1; j &gt; 0; j--) {
                    System.out.print(binnum[j]);
                }
            }
        } else {
            System.out.println(&quot;ERROR: Invalid Input&quot;);
            System.out.print(&quot;Enter a number: &quot;);
        }
    }

答案2

得分: 1

根据您的评论，我已经更新了程序，允许仅接受在十六进制范围为90至FF的数字。

请按照以下步骤操作：

import java.util.Scanner;

public class Main {
    public static int hex2decimal(String s) {
        String digits = "0123456789ABCDEF";
        s = s.toUpperCase();
        int val = 0;
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            int d = digits.indexOf(c);
            val = 16 * val + d;
        }
        return val;
    }

    public static void main(String args[]) {
        String hexdecnum;
        int decnum, i = 1, j;

        int binnum[] = new int[100];
        Scanner scan = new Scanner(System.in);
        boolean valid;
        do {
            valid = true;
            System.out.print("Enter Hexadecimal number in the range of 90 to FF: ");
            hexdecnum = scan.nextLine();
            final int MAX_LENGTH = 2;

            if (hexdecnum.matches("[A-Fa-f0-9]{2}") && hex2decimal(hexdecnum) >= 144) {
                /* first convert the hexadecimal to decimal */

                decnum = hex2decimal(hexdecnum);
                System.out.print("Equivalent Dec Number is : " + decnum);
                System.out.println();

                /* now convert the decimal to binary */

                while (decnum != 0) {
                    binnum[i++] = decnum % 2;
                    decnum = decnum / 2;
                }

                System.out.print("Equivalent Binary Number is : ");
                for (j = i - 1; j > 0; j--) {
                    System.out.print(binnum[j]);
                }
            } else {
                System.out.println("ERROR: Invalid Input");
                valid = false;
            }
        } while (!valid);
    }
}

示例运行：

Enter Hexadecimal number in the range of 90 to FF: abc
ERROR: Invalid Input
Enter Hexadecimal number in the range of 90 to FF: ab
Equivalent Dec Number is : 171
Equivalent Binary Number is : 10101011

Enter Hexadecimal number in the range of 90 to FF: AG
ERROR: Invalid Input
Enter Hexadecimal number in the range of 90 to FF: AB
Equivalent Dec Number is : 171
Equivalent Binary Number is : 10101011

Enter Hexadecimal number in the range of 90 to FF: 21
ERROR: Invalid Input
Enter Hexadecimal number in the range of 90 to FF: 90
Equivalent Dec Number is : 144
Equivalent Binary Number is : 10010000

Enter Hexadecimal number in the range of 90 to FF: 40
ERROR: Invalid Input
Enter Hexadecimal number in the range of 90 to FF: FF
Equivalent Dec Number is : 255
Equivalent Binary Number is : 11111111

如果有任何疑问/问题，请随时进行评论。

英文翻译

Based on your comment, I have updated the program to allow accepting a number only in the hexadecimal range of 90 to FF.

Do it as follows:

import java.util.Scanner;

public class Main {
	public static int hex2decimal(String s) {
		String digits = &quot;0123456789ABCDEF&quot;;
		s = s.toUpperCase();
		int val = 0;
		for (int i = 0; i &lt; s.length(); i++) {
			char c = s.charAt(i);
			int d = digits.indexOf(c);
			val = 16 * val + d;
		}
		return val;
	}

	public static void main(String args[]) {
		String hexdecnum;
		int decnum, i = 1, j;

		int binnum[] = new int[100];
		Scanner scan = new Scanner(System.in);
		boolean valid;
		do {
			valid = true;
			System.out.print(&quot;Enter Hexadecimal number in the range of 90 to FF: &quot;);
			hexdecnum = scan.nextLine();
			final int MAX_LENGTH = 2;

			if (hexdecnum.matches(&quot;[A-Fa-f0-9]{2}&quot;) &amp;&amp; hex2decimal(hexdecnum) &gt;= 144) {
				/* first convert the hexadecimal to decimal */

				decnum = hex2decimal(hexdecnum);
				System.out.print(&quot;Equivalent Dec Number is : &quot; + decnum);
				System.out.println();

				/* now convert the decimal to binary */

				while (decnum != 0) {
					binnum[i++] = decnum % 2;
					decnum = decnum / 2;
				}

				System.out.print(&quot;Equivalent Binary Number is : &quot;);
				for (j = i - 1; j &gt; 0; j--) {
					System.out.print(binnum[j]);
				}
			} else {
				System.out.println(&quot;ERROR: Invalid Input&quot;);
				valid = false;
			}
		} while (!valid);
	}
}

A sample run:

Enter Hexadecimal number in the range of 90 to FF: abc
ERROR: Invalid Input
Enter Hexadecimal number in the range of 90 to FF: ab
Equivalent Dec Number is : 171
Equivalent Binary Number is : 10101011

Another sample run:

Enter Hexadecimal number in the range of 90 to FF: AG
ERROR: Invalid Input
Enter Hexadecimal number in the range of 90 to FF: AB
Equivalent Dec Number is : 171
Equivalent Binary Number is : 10101011

Another sample run:

Enter Hexadecimal number in the range of 90 to FF: 21
ERROR: Invalid Input
Enter Hexadecimal number in the range of 90 to FF: 90
Equivalent Dec Number is : 144
Equivalent Binary Number is : 10010000

Another sample run:

Enter Hexadecimal number in the range of 90 to FF: 40
ERROR: Invalid Input
Enter Hexadecimal number in the range of 90 to FF: FF
Equivalent Dec Number is : 255
Equivalent Binary Number is : 11111111

Feel free to comment in case of any doubt/issue.

huangapple
  • 本文由 发表于 2020年3月17日 03:24:27
  • 转载请务必保留本文链接：https://java.coder-hub.com/60712078.html
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