CSE2056532

If the user enters: 123

What does the program below output?

import java.util.Scanner;
import java.util.InputMismatchException;

public class Main {
public static void main(String[] args) {
Scanner scnr = new Scanner(System.in);
int num = 0;

try {
num = scnr.nextInt();
System.out.print("Good! ");
}
catch (InputMismatchException e) {
System.out.print("Bad! ");
}

System.out.print(num);
}
}

Question

CSE2056532

If the user enters: 123

What does the program below output?

import java.util.Scanner;
import java.util.InputMismatchException;

public class Main {
   public static void main(String[] args) {
      Scanner scnr = new Scanner(System.in);
      int num = 0;

try {
         num = scnr.nextInt();
         System.out.print("Good! ");
      } 
      catch (InputMismatchException e) {
         System.out.print("Bad! ");
      }

System.out.print(num);
   }
}

BlackTom AI · Accepted Answer

Scanner.nextInt() attempts to read an integer token; when it successfully parses one it returns that int and does not throw InputMismatchException.

Relevant concepts:
- Scanner.nextInt() reads the next token as an int and throws InputMismatchException only if the token cannot be parsed as an int.
- The try block executes its statements when no exception is thrown; the catch block runs only on an InputMismatchException.
- num is initialized to 0, then reassigned inside the try if parsing succeeds.
- System.out.print prints exactly what is given, with the prints occurring in sequence on the same line.

Step-by-step execution with input "123":
1. num is initialized to 0.
2. The program enters the try block and calls scnr.nextInt(). The user-entered token "123" is a valid integer, so nextInt() returns the int value 123.
3. num = 123 executes, updating num from 0 to 123.
4. System.out.print("Good! "); executes, producing the string "Good! " (note the trailing space).
5. Because no exception occurred, the catch block is skipped.
6. After the try-catch, System.out.print(num); executes, printing the numeric value 123 immediately after the previous output. Because the earlier print included a space, the combined output is "Good! 123".

Why the correct choice is correct:
- The successful parse leads to the try branch output ("Good! ") followed by printing the assigned num (123), therefore "Good! 123".

Why the other options are incorrect:
- "Bad!" and "Bad! 123" would require an InputMismatchException; that does not occur for input "123".
- "Good!" alone omits the subsequent print of num.
- "123" alone omits the "Good! " printed in the try.
- "None of these" is incorrect because one of the provided choices matches the actual output.

Conclusion: The program prints Good! 123, which matches the provided correct answer.

类似问题

A project has a required return of 12.6 percent, an initial cash outflow of $42,100, and cash inflows of $16,500 in Year 1, $11,700 in Year 2, and $10,400 in Year 4. What is the net present value?

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