Access ArrayList of Objects
What code do i need to have in order to access the object inside the array list and print each element from that object.
import java.io.*;
import java.util.ArrayList;
class Board
{
publicstaticvoid main (String[] args)
{
ArrayList myList =new ArrayList ();
Player p1 =new Player (100,"jack","fast");
myList.add (p1);
}
}
class Player
{
privateint score;
private String name;
private String power;
public Player (int score, String name, String power)
{
this.score = score;
this.name = name;
this.power = power;
}
}
[1419 byte] By [
Wulda] at [2007-11-27 6:38:20]
private void foo(ArrayList myList){
Player player;
for(Object obj: myList){
player = (Player)obj;
System.out.println("Score: " + player.score);
System.out.println("Name: " + player.name);
System.out.println("Power: " + player.power);
}
}
Not very elegant but works... my first enhanced for loop woohoooo :-)
hope this helps...
If you are using Java 1.5 or above then you can do the following to prevent casting.
import java.util.ArrayList;
import java.util.List;
class Board
{
public static void main (String[] args)
{
List<Player> myList = new ArrayList<Player> (); //Specify type to save casting
Player p1 = new Player (100, "jack", "fast");
myList.add (p1);
System.out.println(myList.get(0).getName());
}
}
class Player
{
private int score;
private String name;
private String power;
public Player (int score, String name, String power)
{
this.score = score;
this.name = name;
this.power = power;
}
public String getName() {
return name;
}
public String getPower() {
return power;
}
public int getScore() {
return score;
}
}
Also, maybe consider expressing power with a numerical value which will be might be more flexible depending on your needs.
Thank you _helloWorld_ for making my inelegant code more elegant :-)
The improved version:
private static void foo(ArrayList<Player> myList){
for(Player player: myList){
System.out.println("Score: " + player.score);
System.out.println("Name: " + player.name);
System.out.println("Power: " + player.power);
}
}
class Player {
// ...
public String toString() {
return "Name: " + name + "\n Power: " + power + "\n Score: " + score;
}
}
// ...
for (Player player : myList) {
System.out.println(player);
}
Even better. I stand in awe!
> Even better.Yep, it is rare that I think to override the toString method to something useful.
import java.io.*;
import java.util.ArrayList;
class Board
{
public static void main (String[] args)
{
ArrayList<Player> myList = new ArrayList<Player> ();
Player p1 = new Player (100, "jack", "fast");
myList.add (p1);
for(Player p:myList)
System.out.println(p);
}
}
class Player
{
private int score;
private String name;
private String power;
public Player (int score, String name, String power)
{
this.score = score;
this.name = name;
this.power = power;
}
public String toString() {
return ""+name+" "+score+" "+power;
}
}
eaajea at 2007-7-12 18:06:57 >
List<Player> myList = new ArrayList<Player> (); //Specify type to save casting
Player p1 = new Player (100, "jack", "fast");
myList.add (p1);
System.out.println(myList.get(0).getName());
What are <Player> for? When i try running the program there is an error on that line.
Also, there is an error on the println ( message says, "No method named "getName" was found in type "java.lang.Object")
Wulda at 2007-7-12 18:06:57 >
> List<Player> myList = new ArrayList<Player> ();
> //Specify type to save casting
>
> Player p1 = new Player (100, "jack", "fast");
>
> st.add (p1);
>
> ystem.out.println(myList.get(0).getName());
>
>
> What are <Player> for? When i try running the program
> there is an error on that line.
>
> Also, there is an error on the println ( message
> says, "No method named "getName" was found in type
> "java.lang.Object")
I think you are using a JDK which is older than version 1.5. If that is true then use the method described in reply # 1.
If you are using JDK 1.5 or higher then please post your code and the exception being generated so someone can help you out.
Thanks.
EDIT: <Player> is an example of generics in Java. It forces a compile time checking of the type of objects you are adding to a collection like ArrayList. You can read about it more over here:
http://java.sun.com/j2se/1.5.0/docs/guide/language/generics.html
However, generics were introduced in Java 1.5. If you have an older JDK, generics wouldn't work.
Message was edited by:
DarumA
I'm using (Ready to Program 1.7 using Java 1.4.2).
I have tried the first way but there is an error so i guess i didn't use it the right way.
error: for(Object obj: myList) // says "misplaced construct(s)"
import java.util.ArrayList;
class Board
{
public static void main (String[] args)
{
ArrayList myList = new ArrayList ();
Player p1 = new Player (100, "jack", "fast");
myList.add (p1);
foo (myList);
}
private void foo(ArrayList myList)
{
Player player;
for(Object obj: myList)
{
player = (Player)obj;
System.out.println("Score: " + player.score);
System.out.println("Name: " + player.name);
System.out.println("Power: " + player.power);
}
}
}
class Player
{
private int score;
private String name;
private String power;
public Player (int score, String name, String power)
{
this.score = score;
this.name = name;
this.power = power;
}
}
Wulda at 2007-7-12 18:06:57 >
Seems like the enhanced for loop doesnt work below JDK 1.5 either. Strange I thought it was introduced in JDK1.4. Anyways below is the JDK1.4 compatible code:
import java.util.ArrayList;
import java.util.*;
class Board
{
public static void main (String[] args)
{
ArrayList myList = new ArrayList ();
Player p1 = new Player (100, "jack", "fast");
Player p2 = new Player (20, "tom", "slow");
myList.add (p1);
myList.add(p2);
foo (myList);
}
private static void foo(ArrayList myList)
{
Player player;
Iterator i = myList.iterator();
while(i.hasNext()){
player = (Player)i.next();
System.out.println("Score: " + player.score);
System.out.println("Name: " + player.name);
System.out.println("Power: " + player.power);
}
}
}
class Player
{
protected int score;
protected String name;
protected String power;
public Player (int score, String name, String power)
{
this.score = score;
this.name = name;
this.power = power;
}
}
Thank you all for the time and help.
Wulda at 2007-7-12 18:06:57 >
