Programming Forums > Application Development > Java

Writlaus · Nov 30th, 2005, 8:22 PM

I started in Java a bit ago, and I was wondering: are there any functions similar to PHP's array_push() and array_pop() methods? If not, is there another variable type I should use if the length of the array will change?

Mjordan2nd · Nov 30th, 2005, 9:19 PM

I think you would find ArrayLists to be useful for you.

http://java.sun.com/j2se/1.4.2/docs/...ArrayList.html

titaniumdecoy · Nov 30th, 2005, 10:00 PM

You can't resize arrays in Java.

I was wondering, though, is there any way to store a basic data type such an int or double in a ListArray or any other type of array/list rathern than an Integer or Double object?

andro · Nov 30th, 2005, 10:57 PM

Quote:

Originally Posted by titaniumdecoy

You can't resize arrays in Java.

I was wondering, though, is there any way to store a basic data type such an int or double in a ListArray or any other type of array/list rathern than an Integer or Double object?

Make sure to import java.util.ArrayList.

(Toggle Plain Text)

ArrayList<Integer> myList = new ArrayList<Integer>();

and the ArrayList api...
http://java.sun.com/j2se/1.5.0/docs/...ArrayList.html

titaniumdecoy · Dec 1st, 2005, 2:38 PM

Quote:

Originally Posted by andro

Make sure to import java.util.ArrayList.

(Toggle Plain Text)

ArrayList<Integer> myList = new ArrayList<Integer>();

and the ArrayList api...
http://java.sun.com/j2se/1.5.0/docs/...ArrayList.html

Thanks for your help. Is it possible to do the equivalent of this but store primitive int data types, for example ArrayList<int>? I looked up "autoboxing" but I'm not sure that's what I want. I need something that will run very fast, which is why I don't want to have to keep converting from Integer to int and so forth.

Writlaus · Nov 30th, 2005, 10:03 PM

Thanks for the link, I do appreciate it.

Writlaus · Nov 30th, 2005, 10:24 PM

This is no doubt a product of the fact that I'm new to Java, but...

How do I create an ArrayList? It says it can't find the class ArrayList when I try to initialize it like I would another object type.

groovicus · Nov 30th, 2005, 10:39 PM

Don't take this at all the wrong way, but have are you familiar with the Java api? You are possibly not declaring it properly, or do not have the proper library imported. Check here:
http://java.sun.com/j2se/1.5.0/docs/...ArrayList.html

If you have a difficult time with it, just ask. They are a little difficult to understand at first (they were for me anyway). But it will tell you all you need to know.

Writlaus · Dec 1st, 2005, 2:56 AM

I'm sure I'm making it painfully obvious I'm new to Java.

What I'm trying to use the ArrayList for is to keep track of dot objects in my applet. Dots are going to be created by the user with every click, which is why I needed to be able to add elements to it.

My problem now is that when I use the ArrayList.get(int index) method, I can't use that to access the object's variables. Here are some parts of my code...

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    public class MyPoint {
        int x,y;
        public MyPoint(int x1,int y1) {
            x=x1;y=y1;
        }
    }

(Toggle Plain Text)

    ArrayList points=new ArrayList();

(Toggle Plain Text)

    public boolean mouseDown(Event e, int x, int y) {
        points.add(new MyPoint(x,y));
        return false;
    }

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    public void paint(Graphics g) {
        g.setColor(Color.black);
        g.fillRect(0,0,windowWidth,windowHeight);
        g.setColor(Color.blue);
        for(int i=0;i<points.size();i++) {
            g.fillOval(points.get(i).x,points.get(i).y,dotSize,dotSize);
        }
    }

In that last bit, g.fillOval(points.get(i).x,points.get(i).y,dotSize,dotSize); cannot find x...

*Sigh* I know I'm new to Java, and I'm sure it's something simple I have wrong.

groovicus · Dec 1st, 2005, 7:14 AM

What kind of error is it giving you?

Nov 30th, 2005, 8:22 PM	#1
Writlaus Hobbyist Programmer Join Date: Nov 2005 Posts: 149 Rep Power: 3	Java array functions? I started in Java a bit ago, and I was wondering: are there any functions similar to PHP's array_push() and array_pop() methods? If not, is there another variable type I should use if the length of the array will change?

Nov 30th, 2005, 9:19 PM	#2
Mjordan2nd The Supreme Ruler Join Date: May 2004 Location: Houston Posts: 1,476 Rep Power: 6	I think you would find ArrayLists to be useful for you. http://java.sun.com/j2se/1.4.2/docs/...ArrayList.html __________________ "Every gun that is made, every warship launched, every rocket signifies, in the final sense, a theft from those who hunger and are not fed, from those who are cold and are not clothed. The world in arms is not spending money alone. It is spending the sweat of its laborers, the genius of its scientists, the hopes of its children." - Dwight D. Eisenhower

Nov 30th, 2005, 10:39 PM	#8
groovicus Programmer Join Date: Nov 2004 Posts: 84 Rep Power: 4	Don't take this at all the wrong way, but have are you familiar with the Java api? You are possibly not declaring it properly, or do not have the proper library imported. Check here: http://java.sun.com/j2se/1.5.0/docs/...ArrayList.html If you have a difficult time with it, just ask. They are a little difficult to understand at first (they were for me anyway). But it will tell you all you need to know. __________________ HijackThis Team-SFDC

Dec 1st, 2005, 2:56 AM	#9
Writlaus Hobbyist Programmer Join Date: Nov 2005 Posts: 149 Rep Power: 3	I'm sure I'm making it painfully obvious I'm new to Java. What I'm trying to use the ArrayList for is to keep track of dot objects in my applet. Dots are going to be created by the user with every click, which is why I needed to be able to add elements to it. My problem now is that when I use the ArrayList.get(int index) method, I can't use that to access the object's variables. Here are some parts of my code... (Toggle Plain Text) public class MyPoint { int x,y; public MyPoint(int x1,int y1) { x=x1;y=y1; } } public class MyPoint { int x,y; public MyPoint(int x1,int y1) { x=x1;y=y1; } } (Toggle Plain Text) ArrayList points=new ArrayList(); ArrayList points=new ArrayList(); (Toggle Plain Text) public boolean mouseDown(Event e, int x, int y) { points.add(new MyPoint(x,y)); return false; } public boolean mouseDown(Event e, int x, int y) { points.add(new MyPoint(x,y)); return false; } (Toggle Plain Text) public void paint(Graphics g) { g.setColor(Color.black); g.fillRect(0,0,windowWidth,windowHeight); g.setColor(Color.blue); for(int i=0;i<points.size();i++) { g.fillOval(points.get(i).x,points.get(i).y,dotSize,dotSize); } } public void paint(Graphics g) { g.setColor(Color.black); g.fillRect(0,0,windowWidth,windowHeight); g.setColor(Color.blue); for(int i=0;i<points.size();i++) { g.fillOval(points.get(i).x,points.get(i).y,dotSize,dotSize); } } In that last bit, g.fillOval(points.get(i).x,points.get(i).y,dotSize,dotSize); cannot find x... Sigh I know I'm new to Java, and I'm sure it's something simple I have wrong.

Dec 1st, 2005, 7:14 AM	#10
groovicus Programmer Join Date: Nov 2004 Posts: 84 Rep Power: 4	What kind of error is it giving you? __________________ HijackThis Team-SFDC

Nov 30th, 2005, 10:00 PM	#3
titaniumdecoy Expert Programmer Join Date: Nov 2005 Posts: 855 Rep Power: 3	You can't resize arrays in Java. I was wondering, though, is there any way to store a basic data type such an int or double in a ListArray or any other type of array/list rathern than an Integer or Double object?

Nov 30th, 2005, 10:03 PM	#6
Writlaus Hobbyist Programmer Join Date: Nov 2005 Posts: 149 Rep Power: 3	Thanks for the link, I do appreciate it.

Nov 30th, 2005, 10:24 PM	#7
Writlaus Hobbyist Programmer Join Date: Nov 2005 Posts: 149 Rep Power: 3	This is no doubt a product of the fact that I'm new to Java, but... How do I create an ArrayList? It says it can't find the class ArrayList when I try to initialize it like I would another object type.

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Programming Forums > Application Development > Java

Java array functions?