rectcollection.java

书籍"Java_面向事件编程"的附带光盘代码

import objectdraw.*;

// maintains a collection of FilledRects

public class RectCollection {
    
    // the array used to hold the rectangles
    private FilledRect[] theRects;
    
    // the number of rectangles currently in the array
    private int curCount = 0;
    
    // Create a collection that can hold 'size' rectangles
    public RectCollection( int size){
        theRects = new FilledRect[size];
    }
    
    // add a new rectangle to the collection (if there is room)
    public void add(FilledRect newRect){
        if ( curCount < theRects.length){
            theRects[ curCount ] = newRect;
            curCount++;
        } else {
            System.out.println("Too many rects in collection");
        }
    }
    
    // return a rectangle in the collection that overlaps with the ball
    // or return null 
    public FilledRect findFirstOverlap(FilledOval ball){
        for ( int pos = 0; pos < curCount; pos++) {
            if ( ball.overlaps(theRects[pos])) {
                return theRects[pos];
            }
        }
        return null;
    }
    
    // the following methods provide the means to step through the
    // collection of rectangles processing all of its members
    // in sequence
    
    // position of next rectangle to process
    private int curRect;
    
    // start processing with the first rectangle in the collection
    public void goToFirst() {
        curRect = 0;
    }
    
    // return true if there are more rectangles left to process
    public boolean rectsLeft(){
        return curRect < curCount;
    }
    
    // return the next rectangle to process
    public FilledRect getNextRect() {
        if ( rectsLeft() ) {
            curRect++;
            return theRects[curRect-1];
        } else {
            return null;
        }
    }
    
    // ----------  end of methods for processing rects sequentially 
    
    // return a rectangle that overlaps the ball and remove it from the
    // collection, otherwise return null
    public FilledRect removeFirstOverlap(FilledOval ball){
        for ( int pos = 0; pos < curCount; pos++) {
            if ( ball.overlaps(theRects[pos])) {
                FilledRect result = theRects[pos];
                removeRect(pos);
                return result;
            }
        }
        return null;
    }
    
    public void removeRect(int pos){
        theRects[pos] = theRects[curCount-1];
        curCount--;
    }
    
    
    
    /*   alternate way to remove rectangle from the collection
         for (int target = pos; target < curCount-1; target++){
           theRects[target] = theRects[target+1];
         }
    */
    
    
    
}