1.3任意の実数を出力する

public class test {



    public static void printDigit(int n){

        System.out.print(n);

    }

    

    public static void printInt(int n){

        if(n>=10){

            printInt(n/10);

        }

        printDigit(n%10);

    }

    public static int getInt(double n){

        return (int)n;

    }

    public static double getFraction(double n){

        return (n-(int)n);

    }

    public static void printFraction(double fraction,int dec){

        int i,tmp;

        for(i=0;i<dec;i++){

            fraction = fraction *10;

            tmp = getInt(fraction);

            printDigit(tmp);

            fraction = getFraction(fraction);

        }

    }

    public static double runUp(double n,int dec){

        int i;

        double tmp = 0.5;

        for(i =0;i<dec;i++){

            tmp = tmp / 10;

        }

        return (n + tmp);

    }

    public static void printReal(double n,int dec){

        int tmp1;

        double tmp2;

        if(n<0)

            n = -n;

        n = runUp(n,dec);

        tmp1 = getInt(n);

        tmp2 = getFraction(n);

        printInt(tmp1);

        if(dec > 0){

            System.out.print(".");

            printFraction(tmp2,dec);

        }

    }

    public static void main(String[] args) {

        // TODO Auto-generated method stub

        printReal(4.65,2);

    }

}

注意:runUp関数、そうでないと出力と必ずしも一致しません.