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POArraylist of type superclass to hold various subclass types
 

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    <p>The functions in my classes have worked after being tested. The ColorDrop creates a falling drop of specified color. The SpeedDrop of specified speed and so forth. I want to put my drops in a list an mass produce them in the GUI. Drop is the superclass, ColorDrop and SpeedDrop are subclasses that extend the superclass. The code compile, but the GUI is blank. Am i assembling my arraylist wrong? Or am I calling methods on objects of that list incorrectly?</p> <pre><code> package advancedobject; import java.awt.Color; import java.awt.Graphics2D; import java.util.ArrayList; public class MyGooDrop extends Goo { Drop testDrop; Drop colorDrop; Drop fastDrop; Drop wavyDrop; int random = (int) Math.random()*width; ArrayList&lt;Drop&gt; drops; public MyGooDrop() { testDrop = new Drop(width/2, -10, 10); colorDrop = new ColorDrop(width/3, -10, 10, Color.BLUE); fastDrop = new SpeedDrop ( (width * 3/4), -10, 10, 5); wavyDrop = new WavyDrop (-10, height/2, 10); drops = new ArrayList&lt;Drop&gt;(); fillDropList(); } public void fillDropList () { for(int i = 0; i&lt;= 12; i++) { if (i &lt;= 4) drops.add(i, new Drop ((int) Math.random()*width, -10, 10)); else if (i&gt;4 &amp;&amp; i&lt;=8) drops.add(i, new ColorDrop ((int) Math.random()*width, -10, 10, Color.BLUE)); //drops.get(i).randomPainter() else drops.add(i, new SpeedDrop ((int) Math.random()*width, -10, 10, (int) Math.random()*10)); } } public void draw(Graphics2D g) { // Fill background g.setColor(Color.GRAY); g.fillRect(0, 0, width, height); testDrop.draw(g); colorDrop.draw(g); fastDrop.draw(g); wavyDrop.draw(g); for(int i = 0; i&lt;=12; i++) drops.get(i).draw(g); } public void update(){ testDrop.move(width, height); colorDrop.move(width, height); fastDrop.move(width, height); wavyDrop.move(width, height); for(int i = 0; i&lt;=12; i++) drops.get(i).move(width, height); } public static void main(String[] args) { MyGooDrop tester = new MyGooDrop(); tester.go(); } } </code></pre>
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    1. USFred V
    1. USFred V
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      1. VTDownMod
    1. COYou don't need to cast to `Drop` when adding to the list, since all items you add inherit it
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      1. USfge
    2. COit doesn't work without the cast either :\
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    3. COThe cast to `Drop` is completely unnecessary.
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      1. USYuushi
 

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