Java - passing an object array to a method?

dlofnep

I have a class, one of the methods creates an array of objects. The size of the array is specified by another method. I might be going about this arseways, but this is the only way I can see. Anywho..

pAdd method.

public static void pAdd(int cellCount){
	Prisoner[] p = new Prisoner[cellCount];
	for(int i = 0; i < p.length; i++){
		System.out.print("Inmate's forename: " );
		p[i].firstName = Keyboard.readString();
		System.out.print("Inmate's surname: " );
		p[i].surName = Keyboard.readString();
		System.out.print("Inmate's age: " );
		p[i].age = Keyboard.readInt();
		System.out.print("Inmate's forename: " );
		p[i].sentence = Keyboard.readInt();
		// automatically assign cell id.
		p[i].cellNum = i;
	}
}

Note (cellCount is being passed to the array to count the number of cells).

So, I'm trying to pass the full p[] array to another method, but it's not passing.

pDetails method

public static void pDetails(p[]){
	System.out.print("Enter prisoner ID: ");
	int i = Keyboard.readInt();
	System.out.println("Prisoner details.");
	System.out.println("Cell ID: " + p[i].cellNum);
	System.out.println("Cell ID: " + p[i].firstName);
	System.out.println("Cell ID: " + p[i].surName);
	System.out.println("Cell ID: " + p[i].age);
	System.out.println("Cell ID: " + p[i].sentence);
}

The output error is: G:\Year 2\Server Scripting\Assignment 1\menuOption.java:59: <identifier> expected
public static void pDetails(p[]){

Here is my prisoner class just incase.

Prisoner class.

public class Prisoner{

// variables
int cellNum;
String firstName;
String surName;
int age;
int sentence;

// constructor
Prisoner(int cellNum, String firstName, String surName, int age, int sentence){
	this.cellNum = cellNum;
	this.firstName = firstName;
	this.surName = surName;
	this.age = age;
	this.sentence = sentence;
}


}

Ideally, I just want to pass the array to printing method just so I can print out a select prisoner details.

Any help would be great.

John.

eden_my_ass

Didn't read through the rest of your code but it seems your immediate problem is that you haven't declared that parameter right....

public static void pDetails(p[]){

should be...

public static void pDetails(Prisoner[] p){

I think

ianhobo

yep, i agree
You didn't specify any type for the array that your passing in.
So the comipler doesn't know if its an array of chars, ints, type object, elephants, or an array of objects of type prisoner

dlofnep

Ah yes! Thanks, you're correct.

dlofnep

Eek, now I'm getting an error with my switch menu when I call two methods (menuOption.pAdd() and menuOption.pDetails())

Error message:
pAdd(Prisoner[]) in menuOption cannot be applied to ()
menuOption.pAdd();

pDetails(Prisoner[]) in menuOption cannot be applied to ()
menuOption.pDetails();

Sorry for all the questions, we covered objects in 40 minutes last year so I'm not totally up on all the rules - I'm the only one in class who even has an idea where to begin on this program, it's far beyond the scope of what we covered last year


Switch menu code

public static void showSwitches(){
	int i = 0;
	i = Keyboard.readInt();


	/*
	user menu methods
	see menuOption.java to see past method abstraction
	*/

	switch(i){

		case 1:
			menuOption.pAdd();
		break;

		case 2:
			menuOption.listOldest();
		break;

		case 3:
			menuOption.listYoungest();
		break;

		case 4:
			menuOption.listSentence();
		break;

		case 5:
			menuOption.listAverage();
		break;

		case 6:
			menuOption.pDetails();
		break;

		default:
			System.out.println("Invalid option selected.");
		break;
		}
	}

Other

public class menuOption{

Prisoner[] p; // create prisoner object


// list youngest prisoner.
public static void listYoungest(){
		System.out.println("Youngest prisoner is: ");
	}

// construct prison size
public static void constructCells(Prisoner[] p){
		int cellCount;
		System.out.print("How many cells do you require: ");
		cellCount = Keyboard.readInt();
		System.out.println(cellCount + " cells constructed.");
		p = new Prisoner[cellCount];
	}


// list oldest prisoner
public static void listOldest(){
		System.out.println("Oldest prisoner is: ");
	}


// list longest prison sentence
public static void listSentence(){
		System.out.println("Longest sentence is: ");
	}


// list average prisoner age
public static void listAverage(){
		System.out.println("Average age is: ");
	}


// add a prisoner to the database
public static void pAdd(Prisoner[] p){
	for(int i = 0; i < p.length; i++){
		System.out.print("Inmate's forename: " );
		p[i].firstName = Keyboard.readString();
		System.out.print("Inmate's surname: " );
		p[i].surName = Keyboard.readString();
		System.out.print("Inmate's age: " );
		p[i].age = Keyboard.readInt();
		System.out.print("Inmate's forename: " );
		p[i].sentence = Keyboard.readInt();
		// automatically assign cell id.
		p[i].cellNum = i;
	}
}

// view prisoner's details
public static void pDetails(Prisoner[] p){
	System.out.print("Enter prisoner ID: ");
	int i = Keyboard.readInt();
	System.out.println("Prisoner details.");
	System.out.println("Cell ID: " + p[i].cellNum);
	System.out.println("Cell ID: " + p[i].firstName);
	System.out.println("Cell ID: " + p[i].surName);
	System.out.println("Cell ID: " + p[i].age);
	System.out.println("Cell ID: " + p[i].sentence);
}

}

hussey

you are trying
menuOption.pAdd();

and you defined the method as
public static void pAdd(Prisoner[] p){

so you are supposed to pass in an object - but you are not

dlofnep

I figured as much - but I have no need to pass it an object when I call the method. I have specified it in the interface of those particular methods because I created the array outside of the method - so I am eseentially bringing the array into the method so I can manipulate it. Have I gone about this all wrong? I won't be able to access the array otherwise will I?

Hobbes

I looked at the first bit of code only. Not sure why you are doing it that way. You would be better to create a bean and access the data that way.

dlofnep

Hobbes wrote: »

I looked at the first bit of code only. Not sure why you are doing it that way. You would be better to create a bean and access the data that way.

It's the only way I know how - we really only covered basic java last year, I had to read up on objects and that myself. But I haven't covered beans. Could you be more specific about which part of the code I am doing awkwardly?

DublinDilbert

dlofnep wrote: »

It's the only way I know how - we really only covered basic java last year, I had to read up on objects and that myself. But I haven't covered beans. Could you be more specific about which part of the code I am doing awkwardly?

Your class "Prisoner" is effectively like an Identity bean...

You could also look at using a Vector to hold the objects of type prisoner... a vector is like an array, just a bit more flexible, you can add and remove objects from it quite easily... Also you can pass the vector between methods, or even over an object stream between 2 computers on a network...

Hobbes

Basically your trying to store data into an array that would be better suited in a bean.

So in the case of the original example you would create a bean as follows.

class InmateBean { 
  private String firstName; 
  private String surName;
  private int age;
  private int cellNumber;

  public void setFirstName(String text) { 
    firstName = text;
  }
 
  public String getFirstName() { 
    return firstName;
  }

  // Do the same for the other fields
}

After that you just create an inmateBean.

InmateBean prisoner = new InmateBean(); 

prisoner.setFirstName("dlofnep");
prisoner.setCell(12);

System.out.println("Cell Number: " + prisoner.getCell());

This way all your related data is contained within an object and can't be manipulated without requesting the data from the object. So for example you could put checks in on setCell so that they can't put a value >20. Data validation goes into the bean.

Looks like you were close though with Prisoner.

After that sending in the value to another function.

public static void pDetails(Prisoner[] p){

dlofnep

I briefly had a look at vectors about two weeks ago. I was going to construct it using vectors, but I figured - why not use an object array and I hadn't enough knowledge about vectors to do it..

So is the problem I have unavoidable with no solution using my current practices? Can I not call that method without supplying a parameter? If I could access the object without specifying it when creating the method, then it wouldn't ask me to supply a parameter when I call it?

dlofnep

Ok thanks Hobbes. I'll give it a crack later.

Giblet

Use an parameterised arraylist.

List<Prisoner> p = new ArrayList<Prisoner>()

Then when you want to add a prisoner go
p.add(prisonerobject).

Then you can call it's details up with p.get(i).WhateverPrisonerMethod

Use a for each loop too.

for(Prisoner myPrisoner: p)
{
myPrisoner.toString();
}

dlofnep

I'll have a look, thanks.