Java進制間轉換

public static void main(String[] args) {
		// TODO Auto-generated method stub
		System.out.println(tenTo16("1000"));
		System.out.println(tenTo8("1000"));
		System.out.println(twoTo10("11111111111111110"));
	}
	public static String tenTo16(String num){
		int ten = Integer.valueOf(num);
		StringBuilder res = new StringBuilder();
		while(ten>0){
			String tmp;
			if(ten %16 == 10){
				tmp = "A";
			}else if(ten %16 == 11){
				tmp = "B";
			}else if(ten %16 == 12){
				tmp = "C";
			}else if(ten %16 == 13){
				tmp = "D";
			}else if(ten %16 == 14){
				tmp = "E";
			}else if(ten %16 == 15){
				tmp = "F";
			}else{
				tmp = ten %16+"";
			}
			res.append(tmp);
			ten /= 16;
		}
		res.reverse();
		return res.toString();
	}
	public static String tenTo8(String num){
		int ten = Integer.valueOf(num);
		StringBuilder res = new StringBuilder();
		while(ten>0){
			res.append(ten%8);
			ten /= 8;
		}
		res.reverse();
		return res.toString();
	}
	public static String twoTo10(String two){
		char[] ch = two.toCharArray();
		int res = 0;
		int j = 0;
		if(ch[ch.length-1] == '1'){
			res = 1;
		}else if(ch[ch.length-1] != '0'){
			return "error";
		}
		for(int i=ch.length-2;i>=0;i--){
			if(ch[i] == '0' || ch[i] == '1'){
				res += Math.pow(2<<j, ch[i]-'0');
				j++;
			}else{
				return "error";
			}
		}
		return res+"";
	}

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