在寫一個排序算法演示程序先在主窗體中的Listener中調(diào)用engine:private class StartListener implements ActionListener{
public void actionPerformed(ActionEvent e){
int[] unsort=UnsortGenerator(); //函數(shù)返回給unsort一個數(shù)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(shù)組
histogram.showHistogram(unsort);//這里會拋出異常
try {
Thread.sleep(sleepTime);
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
}
1 回答

慕斯王
TA貢獻(xiàn)1864條經(jīng)驗 獲得超2個贊
空指針異常在于histogram而不在于unsort
engine中只設(shè)置了array,再設(shè)置上histogram就可以了
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