Java convert decimal to hex

                                    import java.util.Scanner;
public class DecimalToHexaExample 
{
   public static void main(String[] args) 
   {
      Scanner sc = new Scanner(System.in);
      System.out.println("Please enter decimal number: ");
      int decimal = sc.nextInt();
      String strHexadecimal = "";
      while(decimal != 0)
      {
         int hexNumber = decimal % 16;
         char charHex;
         if(hexNumber <= 9 && hexNumber >= 0)
         {
            charHex = (char)(hexNumber + '0');
         }
         else
         {
            charHex = (char)(hexNumber - 10 + 'A');
         }
         strHexadecimal = charHex + strHexadecimal;
         decimal = decimal / 16;
      }
      System.out.println("Hexadecimal number: " + strHexadecimal);
      sc.close();
   }
}

                                    public class DecimalToBinaryExample2{    
public static void toBinary(int decimal){    
     int binary[] = new int[40];    
     int index = 0;    
     while(decimal > 0){    
       binary[index++] = decimal%2;    
       decimal = decimal/2;    
     }    
     for(int i = index-1;i >= 0;i--){    
       System.out.print(binary[i]);    
     }    
System.out.println();//new line  
}    
public static void main(String args[]){      
System.out.println("Decimal of 10 is: ");  
toBinary(10);    
System.out.println("Decimal of 21 is: ");  
toBinary(21);    
System.out.println("Decimal of 31 is: ");    
toBinary(31);  
}}    

                                    public class DecimalToHexExample2{    
public static String toHex(int decimal){    
     int rem;  
     String hex="";   
     char hexchars[]={'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};  
    while(decimal>0)  
     {  
       rem=decimal%16;   
       hex=hexchars[rem]+hex;   
       decimal=decimal/16;  
     }  
    return hex;  
}    
public static void main(String args[]){      
     System.out.println("Hexadecimal of 10 is: "+toHex(10));  
     System.out.println("Hexadecimal of 15 is: "+toHex(15));  
     System.out.println("Hexadecimal of 289 is: "+toHex(289));  
}} 

                                    int integer = 18;

String hexString = Integer.toHexString(integer);