Thread: SIMPLE PROGRAMING PROBLEMS help!!

Please post the code you are having problems with and ask questions about the problems.

I doubt you'll get anyone to do your homework.

public class Unit5Assignment 
{
	public static void main(String [] args)
	{
		int Cartons;
		int N = 37;
		Cartons = N / 12;
		int remainder = N % 12;
		System.out.println("Total number of eggs is " + N);
		System.out.println("Number of cartons needed is " + Cartons);
		System.out.println("Number of eggs left over is " + remainder);
	}
}

// My code for problem 1

When you post code, please wrap your code with
[code=java]
<YOUR CODE HERE>
[/code]
to get highlighting and preserve formatting.

Please explain what your problems are.

use switch statment with logical operators.

There is no connection between a switch statement and logical operators.
You would use logical operators with an if statement.

The normal order of things when writing a program is to figure out the logic for the program and after that is done, see what coding techniques to use to implement the logic. You seem to be worrying about coding techniques before working out the logic.

Please post the contents of the console from when you execute the program showing what you type in and what the program prints out.

You need to compile the code with the -Xlint option. The compiler will give a warning telling you what the problem is: empty statement after if

You should ALWAYS use {}s with if, for and while statements :

  if(var > 4 && another < 3) {
   //  do this if true
  }

Not using them is legal, but you will have problems sometime when you add another statement and forget to add the {}s. Add them immediately when first typing in the if, for and while


Another possible problem is the bitwise & operator. && is the AND operator. See:
Equality, Relational, and Conditional Operators (The Java™ Tutorials > Learning the Java Language > Language Basics)

I'm done for tonight. Back tomorrow.

Here's my new program, it's very similar just changed & to && and put brackets

import java.util.Scanner;
 
public class Unit5Assignment2
{
	public static void main(String [] args)
	{
		Scanner input = new Scanner(System.in);
 
		System.out.println("What is your age?");
		int Age = input.nextInt();
 
		System.out.println("How many insurence claim have you had in the past year?");
		int numClaims = input.nextInt();
 
		if (Age < 25 && numClaims == 0);
		{
			System.out.println("Age = " + Age + "  Claims = " + numClaims + "  Policy Increase = $0");
		}
		if (Age < 25 && numClaims >= 1);
		{
			System.out.println("Age = " + Age + "  Claims = " + numClaims + "  Policy Increase = $100");
		}
		if (Age >= 25 && numClaims == 0);
		{
			System.out.println("Age = " + Age + "  Claims = " + numClaims + "  Policy Increase = $0");
		}
		if (Age >= 25 && numClaims >= 0);
		{
			System.out.println("Age = " + Age + "  Claims = " + numClaims + "  Policy Increase = $50");
		}
	}
}

heres the output
Unit 5 Assignment 2 prob.jpg
maybe i should just take out the input scanner

Did you add the -Xlint option for the javac program so you would get the warning I told you about?
Here is a sample:

Running: D:\Java\jdk1.6.0_29\bin\javac.exe -Xlint  Unit5Assignment2.java
 
Unit5Assignment2.java:19: warning: [empty] empty statement after if
		if (Age < 25 && numClaims == 0);
		                               ^

The ; ends the if statement. Anything following the ; is NOT part of the if statement.

To copy the contents of the command prompt window:
Click on Icon in upper left corner
Select Edit
Select 'Select All' - The selection will show
Click in upper left again
Select Edit and click 'Copy'

Paste here.

javac is an OS command that compiles the source. Commands can take commandline options to control how they work and what they do. -Xlint is a commandline option for the javac command.
The first line (begins with Running: ) of the included text in my post shows the commandline I used to compile your program. See: javac - Java programming language compiler

The & is also a logical operator(otherwise the compiler would give an error message.
The && operator is a short-circuit operator. It stops evaluation when the results are known. See the following. First and last will execute the ++x. The middle one doesn't

 
      int x = 0;
      boolean b1 = (false & ++x >= 0);    // & operator does both tests
      System.out.println("b1="+b1 + ", x=" + x);  // x=1
      boolean b2 = (false && ++x >= 0);              //<<<  && operator ends tests
      System.out.println("b2="+b2 + ", x=" + x);  // x=1   unchanged
      boolean b3 = (false & ++x >= 0);
      System.out.println("b3="+b3 + ", x=" + x);  // x=2

Originally Posted by lightOfDay

& is not a logical operator, strictly.

Well, actually, and strictly, it is when both operands are boolean. This according to the Java Language Specification. (Paragraph 15.22.2 in version 3 of the jls.) Same for '^' and '|'

15.22.2 Boolean Logical Operators &, ^, and |
When both operands of a &, ^, or | operator are of type boolean or Boolean, then
the type of the bitwise operator expression is boolean. In all cases, the operands
are subject to unboxing conversion (§5.1.8) as necessary.

For &, the result value is true if both operand values are true; otherwise, the
result is false.
For ^, the result value is true if the operand values are different; otherwise,
the result is false.
For |, the result value is false if both operand values are false; otherwise,
the result is true.

So, it is not just some squirrelly little thing that "Just Happened." The behavior has been deterministically specified by the author and maintainers of the language.


Cheers!

Z