用来算透明度的。省的每次都要笔算- –

import java.util.Scanner;

public class HexCalculator {
	public static final int HEX = 16;

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		System.out.println("Input a decimal number:");
		int value = in.nextInt();
		System.out.println(calculate(value));
		in.close();

	}
	
	public static char[] calculate(int value) {
		char[] result;
		int numOfBit = 1;
		int hex = HEX;
		while(hex <= value) {
			numOfBit++;
			hex *= HEX;
		}
		int index = 0;
		int left = value;
		result = new char[numOfBit];
		while(numOfBit > 0) {
			numOfBit--;
			hex /= HEX;
			result[index] = calHexBit(left / hex);
			left = value % hex;
			index++;
		}
		return result;
	}
	
	/**
	 * @param value from 0 to 15 decimal number.
	 * @return a char present hex number.
	 */
	public static char calHexBit(int value) {
		switch(value) {
		case 10:
			return 'A';
		case 11:
			return 'B';
		case 12:
			return 'C';
		case 13:
			return 'D';
		case 14:
			return 'E';
		case 15:
			return 'F';
		default:
			return (char) ('0' + value);
		}
	}

}