如何更改打印的方向？

Question

switch (oper){
    case ('A'):
    case ('a'):
        do{
            System.out.print(num%2);
            num=(num/2);
        }while(num>=1);
        break; 
}

So I got this code to convert from decimal to binary, it outputs the result in binary but turned around for example, the number 50 is outputed as 010011 instead of 110010, anyone know a way to turn around the print?

Answer 1

There is no "magic switch" that you can just turn on to print backwards. What you can do, however, is to push all the strings you want to print onto a stack , and then print them as you pop them.

Stack<String> stack = new Stack<>();
do{
    stack.push(Integer.toString(num % 2));
    num=(num/2);
}while(num>=1);
while (!stack.empty()) {
    System.out.println(stack.pop());
}

This works because a stack is a Last In First Out data structure. What gets pushed last gets popped first .

Answer 2

Simply use a StringBuilder https://docs.oracle.com/en/java/javase/13/docs/api/java.base/java/lang/StringBuilder.html#reverse()

StringBuilder str = new StringBuilder();
str.append();
System.out.print(str.reverse().toString());

From your code provided:

StringBuilder str = new StringBuilder();

switch (oper){
    case ('A'):
    case ('a'):
        do{
            str.append(num%2);
            num=(num/2);
        }while(num>=1);
        break; 
}

System.out.print(str.reverse().toString());