Elegant Java

[davoud taghawi]

Hello,

I have an array of a class:

Agent a[] = new Agent[Number_of_Agents];
		for (int i=0;i<Number_of_Agents;i++) {
			a[i]= new Agent();
		}

public class Agent {
	    private double K;
	    private double Y;
	    private double C;
	    private double I;
	    private double s;
            ...

I am looking for an elegant way to calculate the sum of each of this variables over all agents.

Until now I use 4 functions like this:

public class ObjAdd {
	float Y()
	{
	    float Z=0;
	    for (int i=0;i<Number_of_Agents;i++)
	        Z+=Agent[i].Y;   // or Z+=Agent[i].K; or Z+=Agent[i].C ....
	    return Z;
	}
}

Is there an elegant solution?

Davoud

[Sebastian Janisch]

Since you talk about elegant Java, do yourself a favor and use descriptive variable and function names, this makes your code much more readable.

[stanislav bashkirtsev]

Plus show other functions or describe them to make us know what they do.

[fred rosenberger]

do you always need all the sums of all the variables? or are there times when you only need the 'Y' sums?

if it's an all-or-nothing, you might be able to write one method that iterates over the whole array, and keeps a sum for each variable

for (int x = 0 to number of elements)
{
    Ysum += array[x].Y
    Zsum += array[x].Z
    Csum += array[x].C
    ...
}

Then throw all those into an ArrayList (or create an ArrayList initially) and return that.

If you only need ONE sum at a time...not sure there's much else you can do.

[Paul Clapham]

I think the new-style for loop (Java 5) looks much more elegant:

float Y()  
{  
    float Z=0;  
    for (Agent agent: a) 
    {
        Z+=agent.Y;
    }
    return Z;  
}  

[Sunny X Narula]

Hope this looks elegant but again it all depends on what you need

public class Agent {
	
	private double var1;  
    private double var2;  
	private static double sumVar1 = 0;
	private static double multiplyVar2 = 1;
	private static void addVar1(double value) {
		sumVar1 += value;
	}
	
	private static void multiplyVar2(double value) {
		multiplyVar2 *= value;
	}
    
	public Agent(double var1, double var2 ) {
		this.var1 = var1;
		this.var2 = var2;
		addVar1(var1);
		multiplyVar2(var2);
	}
	
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Agent a[] = new Agent[10];  
        for (int i=1;i<10;i++) {  
            a[i]= new Agent(i, i);  
        }  
        System.out.println("Sum over var1 for all instances is: " + Agent.getSumVar1());
        System.out.println("Multiplication over var2 for all instances is: " + Agent.getMulipliedVar2());
	}

	public static double getSumVar1() {
		return sumVar1;
	}

	public static double getMulipliedVar2() {
		return multiplyVar2;
	}

}

[Sebastian Janisch]

I don't like this approach.

Using a static variable to sum everything up means that all instances of the Agent class will be part of the sum. That also includes instances which are created in a totally different spot of the application

[davoud taghawi]

HI,

I took Sunny X Narula solution and modified it so that I can choose the variables to be summed up. Anyway too make this nicer?
What bothers me is that there are five lines in the main routine to get the sum. I would like a solution, where we have to write only one line of code in the main routine, to get the sum of any agent variable.

Thanks Davoud

  
public class Agent {

	public double var1; 
	public double var2;
	private static double sumVar = 0;
	public void addVar1(double value) {
		sumVar += value;
	}
	public Agent(double var1 ) {
		this.var1 = var1;
		this.var2 = var1*2;		
	}
	public static double getSumVar() {
		return sumVar;
	}
	public static void resetSumVar() {
		sumVar=0;
	}
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Agent a[] = new Agent[10];  
		for (int i=1;i<10;i++) {  
			a[i]= new Agent(i);  
		}  
		for (int i=1;i<10;i++) { 
			a[i].addVar1(a[i].var1);
		}  
		System.out.println("Sum over var1 for all instances is: " + Agent.getSumVar());
		Agent.resetSumVar();
		for (int i=1;i<10;i++) { 
			a[i].addVar1(a[i].var2);
		}  
		System.out.println("Sum over var1 for all instances is: " + Agent.getSumVar());
	}
}