Lecture 7 Objectives

Lecture 7 Objectives [Nov 03]prev next

OPENING LINE: Howard Roark laughed [The Fountainhead, Ayn Rand]

At the end of today's class you should

HAVE READ:

Handout to be provided by professor (online)

KNOW:

The concept of a function
The concept of a parameter
The concept of an argument
The return type of a function

BE ABLE TO:

Write a function with no parameters that returns a value
Write a function with a single int parameter that returns twice the value of the parameter. Demonstrate its use on the int 18.

Explain why the following program, when run, prints out the numbers 5 7 5 7, one per line.

package nov03;

public class AttemptSwap {
  /** Incorrect method to swap variable values. */
  public static void swap (int x, int y) {
    int t = x;
    x = y;
    y = t;
  }
	
  /** Incorrect program to show how to swap variable values. */
  public static void main (String []args) {
    // INPUT
    int a = 5;
    int b = 7;
		
    System.out.println (a);
    System.out.println (b);
		
    // try to swap values (INCORRECT)
    swap (a,b);
		
    System.out.println (a);
    System.out.println (b);
  }
}

DAILY QUESTION:

What is wrong with the way that the following method is defined:

public static String evaluate(int x) {
    if (x < 10) {
       return "low";
    }
}

Sample Exam Question:

Write a program where the user types in on a single line a positive number n greater than zero, then types in n numbers separated by spaces followed by pressing Enter. Then output, one per line, each number that had been typed in which was less than 50. In your solution, your main method must be the following (so you must provide the two missing functions).

package nov03;

import java.util.Scanner;

public class SampleQuestion {
  /** Helper methods will appear here. */

	
  /** Incorrect program to show how to swap variable values. */
  public static void main (String []args) {
    Scanner sc = new Scanner(System.in);
    int nums[] = readArray (sc);
    outputLessThan50(nums);
  }
}