为什么输入的数大了就不行了？是什么错误？

Question

import java.util.Scanner;
import static java.lang.Math.pow;
class transformation {
public double A(double x) {
int y = (int) x;
int a, b, c = 1, d, sum = 0;
while (y >= 1) {
a = y / 2;
b = y % 2;
y = a;
d = c * b;
c = c * 10;
sum = sum + d;
}
int i = 1, b1;
double sum1 = 0;
double f = x - (int) x, a1, c1 = 0.1, d1;
while (f != 0) {
a1 = f * 2;
b1 = (int) a1;
f = a1 - b1;
d1 = c1 * b1;
c1 = c1 * 0.1;
sum1 = sum1 + d1;
i++;
if (i == 5) {
break;
}
}
return sum + sum1;
}
public double B(String N) {
double sum = 0;
int j = 1, n = 1;
int pIndex = N.indexOf('.');
if (pIndex == -1) {
for (int i = N.length() - 1; i >= 0; i--) {
int x = N.charAt(i) - '0';
sum = sum + x * pow(2, N.length() - 1 - i);
}
sum = (int) sum;
} else {
for (int i = pIndex + 1; i < N.length(); i++) {
int x = N.charAt(i) - '0';
sum = sum + x * pow(2, pIndex - i);
}
for (int i = pIndex - 1; i >= 0; i--) {
int x = N.charAt(i) - '0';
sum = sum + (int) (x * pow(2, pIndex - i - 1));
}
}
return sum;
}
}
public class Test {
public static void main(String[] args) {
Scanner reader = new Scanner(System.in);
transformation me = new transformation();
System.out.println("请选择操作:1,十进制转二进制 2,二进制转十进制");
int a = reader.nextInt();
for (; a != 1 && a != 2; ) {
System.out.println("输入错误，请重新输入");
a = reader.nextInt();
}
if (a == 1) {
System.out.println("请输入一个十进制数");
double b = reader.nextDouble();
System.out.println("这个数的二进制数为:" + me.A(b));
}
if (a == 2) {
System.out.println("请输入一个二进制数");
String c = reader.next();
System.out.println("这个数的十进制数为:" + me.B(c));
}
}
}

Answer 1

不是不行，是因为你输入的这个小数，转为二进制时小数部分是类似于无限循环小数的