（基础十三）十进制转二进制，八进制，十六进制

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public class decimalToBin {

    public static void main(String[] args) {
        toBin(20);
        toOctal(20);
        toHex(20);
    }

    //十进制-->二进制
    public static void toBin(int num){
        trans(num,1,1);
    }

    //十进制-->八进制
    public static void toOctal(int num){
        trans(num,7,3);
    }

    //十进制-->十六进制
    public static void toHex(int num){
        trans(num,15,4);
    }

    public static void trans(int num,int base,int offset){

        if(num==0)
        {
            System.out.println(0);
            return ;
        }

        char[] chs = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};

        char[] arr = new char[32];

        int pos = arr.length;

        while(num != 0){
            int tmp = num & base;

            arr[--pos] = chs[tmp];

            num = num >>> offset;
        }

        for(int i = pos; i < arr.length; i++){
            System.out.print(arr[i]);
        }

        System.out.println();
    }

}