16進数を変換するときにNumberFormatExceptionが発生する

Question

数値を任意の数値体系（2進/ 10進/ 8進/ 16進）に変換するプログラムを作成しようとしています。プログラム全体は、16進数を2進/ 10進/ 8進数に変換する以外は機能します。ここに私のコード：

import javax.swing.JOptionPane; 

public class convertNumber { 
public static void main(String[] args){ 

    //Getting the numeral system input from the user 
    String numsystem1 = JOptionPane.showInputDialog("Please enter the numeral system that you want to convert FROM: binary, octal, decimal or hexadecimal."); 

    //Validating if the system is written correctly 
    if (numsystem1.equalsIgnoreCase("Binary") || numsystem1.equalsIgnoreCase("Octal") || numsystem1.equalsIgnoreCase("Decimal") || numsystem1.equalsIgnoreCase("Hexadecimal")) 
    {System.out.println ("You are converting from " + numsystem1 + " numeral system:"); 

    //Getting the number input from the user 
    int number = Integer.parseInt (JOptionPane.showInputDialog("Please enter the number that you want to convert.")); 

    //Binary number conversion 
    if (numsystem1.equalsIgnoreCase ("Binary")) { 
     String bin1 = String.valueOf (number); 
     //To decimal 
     int dec1 = Integer.parseInt(bin1,2); 
     //To hexadecimal 
     String hex1 = Integer.toHexString (dec1); 
     //To octal 
     String oct1 = Integer.toOctalString(dec1); 
     System.out.println ("Binary:  " + bin1); 
     System.out.println ("Octal:  " + oct1); 
     System.out.println ("Decimal:  " + dec1); 
     System.out.println ("Hexadecimal: " + hex1); 
    } 

    //Octal number conversion 
    else if (numsystem1.equalsIgnoreCase ("Octal")) { 
     String oct1 = String.valueOf (number); 
     //To decimal 
     int dec1 = Integer.parseInt(oct1,8); 
     //To hexadecimal 
     String hex1 = Integer.toHexString (dec1); 
     //To binary 
     String bin1 = Integer.toBinaryString(dec1); 
     System.out.println ("Octal:  " + oct1); 
     System.out.println ("Binary:  " + bin1); 
     System.out.println ("Decimal:  " + dec1); 
     System.out.println ("Hexadecimal: " + hex1); 
    } 

    //Decimal number conversion 
    else if (numsystem1.equalsIgnoreCase ("Decimal")) { 
     String dec2 = String.valueOf (number); 
     int dec1 = Integer.parseInt(dec2,10); 
     //To binary 
     String bin1 = Integer.toBinaryString(dec1); 
     //To octal 
     String oct1 = Integer.toOctalString (dec1); 
     //To hexadecimal 
     String hex1 = Integer.toHexString (dec1); 
     System.out.println ("Decimal:  " + dec1); 
     System.out.println ("Binary:  " + bin1); 
     System.out.println ("Octal:  " + oct1); 
     System.out.println ("Hexadecimal: " + hex1); 
    } 

    //Hexadecimal number conversion 
    else if (numsystem1.equalsIgnoreCase ("Hexadecimal")) { 
     String hex1 = Integer.toHexString (number); 
     //To decimal 
     int dec1 = Integer.parseInt(hex1); 
     //To binary 
     String bin1 = Integer.toBinaryString(number); 
     //To octal 
     String oct1 = Integer.toOctalString (number); 
     System.out.println ("Hexadecimal: " + hex1); 
     System.out.println ("Binary:  " + bin1); 
     System.out.println ("Octal:  " + oct1); 
     System.out.println ("Decimal:  " + dec1); 
     } 

    else 
    System.out.println ("Please enter the valid system."); 
}}} 

私は間違っている？ hex1以来

Answer 1

は16進数であり、この

int dec1 = Integer.parseInt(hex1); 

はNumberFormatExceptionが、どのように私はそれを修正することができますは何[の

int dec1 = Integer.parseInt(hex1, 16); 

または

String hex1 = Integer.toHexString (number); 
int dec1 = number; // <-- not clear why you need to parse the hex