18. Number Tester Program

Answer:
Yes. There are ways to arrange the tests. You could first split the group into zero and not-zero. 
Then split not-zero into positive and negative. But you will always need two tests, whatever they are.

Number Tester Program

Here is a program that implements the flowchart. The part that corresponds to the nested decision of the flow chart is in red. This is called a nested if statement because it is nested in a branch of an outer if statement.

Indenting: The "false branch" of the first if is a complete if statement. Its two branches are indented relative to the if they belong to.

import java.util.Scanner;

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

    System.out.println("Enter an integer:");
    num = scan.nextInt();

    if ( num < 0 )
    {
      // true-branch
      System.out.println("The number " + num + " is negative");

    } 
    else
    { 
      // nested if
      if ( num > 0 )
      { 
        System.out.println("The number " + num + " is positive"); 
      } 
      else
      {
        System.out.println("The number " + num + " is zero");
      } 

    }

    System.out.println("Good-bye for now");    // always executed
  }
}

Question 18:
Could an if statement be nested inside the true branch of another if statement?