java - 空指针异常在哪里？

Question

这个问题已经有答案了:

What is a NullPointerException, and how do I fix it? (12 个回答)

已关闭 5 年前。

我正在构建一个程序作为CPU进程处理程序，每个进程都有 double 值，进程类中没有静态方法或变量，突发时间是随机生成的，我的方法是将等待时间计算为双计数器，从进程数组中，我将每个进程作为对象添加到 arraylist 中，以将它们添加到 jtable 中，但它在

中给了我一个空指针异常

process1[0].setWaitingtime(waittimecounter + process1[0].getWaitingtime());

为什么会发生这种情况，有人可以给我一个解决方案吗？谢谢这是我的代码

public class start extends javax.swing.JFrame {

    public int processnumber = 100;
    //public int processnumber = 100;
    public int degree = 20;
    public int contextswitch = 2;
    public int timecountom = 10;

    /**
     * Creates new form start
     */
    public start() {
        initComponents();
        addRowToJTable();
    }

    public ArrayList listprocess() {
        ArrayList<process> list = new ArrayList<process>();
        process[] p = new process[processnumber];
        fcfs(p);
        for (int i = 0; i < processnumber; i++) {
            list.add(p[i]);
        }
        return list;
    }

    public void addRowToJTable() {
        DefaultTableModel model = (DefaultTableModel) jTable1.getModel();
        ArrayList<process> list = listprocess();

        Object rowData[] = new Object[4];
        for (int i = 0; i < list.size(); i++) {
            rowData[0] = i;
            rowData[1] = list.get(i).getBursttime();
            rowData[2] = list.get(i).getWaitingtime();
            rowData[3] = list.get(i).getTurnaroundtime();
            model.addRow(rowData);
        }
    }

    public void fcfs(process[] proces) {
        double turnaroundtimecounter = 0;
        double waittimecounter = 0;
        double turnaroundcounter = 0;
        int index = degree - 1;
        double avgwaitingtime = 0;
        double avgturnaroundtime = 0;
        process[] process1 = new process[degree];
        for (int i = 0; i < degree; i++) {
            process1[i] = proces[i];
        }
        //for(int j=0;j<processnumber;j++)
        for (int i = 0; i < processnumber; i++) {
            process1[0].setWaitingtime(waittimecounter + process1[0].getWaitingtime());
            turnaroundcounter = process1[0].getBursttime() + turnaroundcounter;
            process1[0].setTurnaroundtime(turnaroundcounter);
            waittimecounter = process1[0].getBursttime() + waittimecounter;
            proces[i] = process1[0];
            for (int f = 0; f < degree; f++) {
                process1[f] = process1[f + 1];
            }
            if (index < 100) {
                process1[19] = process1[index];
                process1[19].setWaitingtime(-waittimecounter);
                index++;
            }
        }
        avgwaitingtime = waittimecounter / processnumber;
        avgturnaroundtime = turnaroundcounter / processnumber;
    }

Answer 1

您已创建进程数组但从未初始化。