在 do-while 循环中退出程序而没有其他消息 - Java

Question

my code works for what its supposed to do,

do {
    System.out.print("Type a number (or -1 to stop): ");
    
    num = console.nextInt();
    if(num == -1)  
        break;
    
    if (num < min){
        min = num;
    }
    
    if(num > max){
        max = num;
    }
    
} while (true);
System.out.println("Maximum was " + max);
System.out.println("Minimum was " + min);

with the exception of when -1 is the first thing input. if -1 is input with nothing else before the result is this:

Type a number (or -1 to stop): -1
Maximum was -2147483648
Minimum was 2147483647

when it should be:

Type a number (or -1 to stop): -1

I don't know how to do it without max and min being printed in every loop, making the code incorrect for general use.

Answer 1

The easiest way to do it (in terms of the change to your existing code) is just to wrap the System.out.println statements in a conditional:

if (max >= min) {
  System.out.println("Maximum was " + max);
  System.out.println("Minimum was " + min);
}

This works because the condition will only be true if the loop body has executed fully, at least once.

Alternative conditions could include:

• if (max.= Integer.MIN_VALUE) (or whatever you initialize it to)
• if (min.= Integer.MAX_VALUE) (ditto initialization)
• if (min.= Integer.MAX_VALUE && max != Integer.MIN_VALUE)
• Something involving a boolean flag that you set inside the loop when you enter a value other than -1

and many others. But I think just checking that max >= min is the neatest.

Answer 2

You need to keep a counter to know, that at least one valid input has been given.

int counter = 0;
do {
    System.out.print("Type a number (or -1 to stop): ");
    
    num = console.nextInt();
    if(num == -1)  
        break;
    
    if (num < min){
        min = num;
    }
    
    if(num > max){
        max = num;
    }
    counter++;
} while (true);
 if (counter != 0) {
   System.out.println("Maximum was " + max);
   System.out.println("Minimum was " + min);
 }

In case counter remains 0, after ending the loop you know that no valid input has been given, therefore you don't print the max, min

Answer 3

just add an if for your print conditions:

if (min!=-2147483648 && max!=2147483647) {
    System.out.println("Maximum was " + max);
    System.out.println("Minimum was " + min);
}

its not the right way but its the fastest i think