在寫一個排序算法演示程序先在主窗體中的Listener中調用engine：private class StartListener implements ActionListener{ public void actionPerformed(ActionEvent e){ int[] unsort=UnsortGenerator();  //函數返回給unsort一個數組 engine.setArray(unsort); engine.setAlgorithm(getAlgorithm()); engine.setSleepTime(jslSpeed.getValue()*50); engine.setHistogram(histogram);  //Histogram是用來畫柱狀圖的 engine.run(); } }然后在Engine中：private SelectionSort selectionSort=new SelectionSort();...if (thread != null && thread.getState() != Thread.State.TERMINATED) return; thread=new Thread(selectionSort); selectionSort.setArray(unsort); thread.start();在SelectionSort中：public class SelectionSort implements Runnable{ private int[] unsort; private Histogram histogram; private int sleepTime; public void run(){ selectionSort(); } public void setArray(int[] unsort){ this.unsort=unsort; } private void selectionSort(){ int key=0; int count=0; while(count<unsort.length-1){ for(int i=key+1;i<unsort.length;i++){ if(unsort[key]>unsort[i]) key=i; } int temp=unsort[count]; unsort[count]=unsort[key]; unsort[key]=temp; count++; key=count; for(int i=0;i<unsort.length;i++) System.out.printf("%d ",unsort[i]); System.out.print('\n');//這里可以輸出正常數組 histogram.showHistogram(unsort);//這里會拋出異常 try { Thread.sleep(sleepTime); } catch (Exception ex) { ex.printStackTrace(); } } } }