Java primeagechecker的空值

很抱歉发了这么多次。我陷入了为什么结果为空的困境。这应该是真的还是假的。我认为检查值在Employee类中没有链接。 请告诉我问题出在哪里

public class Employee {
    String name;
    PrimeAgeChecker checks;
    int age;
    Department department;
    public ArrayList<Employee> emplo;

    static Employee emp1 = new Employee(Department.Accounting,"Counting Guru",55);
    static Employee emp2 = new Employee(Department.Accounting,"Counting Pro", 45);
    static Employee emp3 = new Employee(Department.Accounting,"Counting Savvy", 40);
    static Employee emp4 = new Employee(Department.Accounting,"Counting Novice", 25);
    static Employee emp5 = new Employee(Department.Marketing,"Sales Guru", 50);
    static Employee emp6 = new Employee(Department.Marketing,"Sales Pro", 48);
    static Employee emp7 = new Employee(Department.Marketing,"Sales Savvy", 38);
    static Employee emp8 = new Employee(Department.Human_Resources,"Hiring Guru", 58);
    static Employee emp9 = new Employee(Department.Human_Resources,"Hiring Pro", 47);
    static Employee emp10 = new Employee(Department.Information_Systems,"Hacking Pro", 46);
    static Employee emp11 = new Employee(Department.Information_Systems,"Hacking Guru", 51);
    static Employee emp12 = new Employee(Department.Information_Systems,"Hacking Savvy", 38);
    static Employee emp13 = new Employee(Department.Information_Systems,"Hacking Novice", 23);

    Employee(Department department,String name, int age)
    {
        this.department = department;
        this.name = name;
        this.age = age;
    }


    public int getAge()
    {
        return age;
    }

    public String getName()
    {
        return name;
    }

    public PrimeAgeChecker GetChecker(PrimeAgeChecker checks)
    {
        return checks;

    }

    public void addEmplo(Employee x){
        if (emplo.isEmpty())
        {
            emplo.add(x);
        }
        else
        {
            int i;
            for ( i = 0;i <emplo.size(); ++i){
                if(emplo.get(i).getAge() > x.getAge()){
                    emplo.add(i,x);
                    break;
                }
            }

            if ( i == emplo.size()){
                emplo.add(x);
            }
        }
        }

    public ArrayList<Employee> getEmplo(){
        return emplo;
    }

    public String toString(){
        StringBuffer sb = new StringBuffer();
        sb.append(getDept(department));
        sb.append("\t");
        sb.append(getName());
        sb.append("\t");
        sb.append(getAge());
        sb.append("\t");
        sb.append(GetChecker(checks));

        return sb.toString();
    }

    private Department getDept(Department department){
        return department;
    }

}




public class PrimeAgeChecker{

    public boolean status = false;

    int ages;

    PrimeAgeChecker(Employee age)
    {
        ages = age.getAge();
    }


    public boolean check(){

            if ((ages % 2 == 0) || (ages == 2))
            {
                status = true;
            }

        return status;

    }
}

---

您从未将变量

checks

设置为任何值，因此当您读取它时，它的值将为

null

我只能猜测您打算在

Employee

构造函数中设置此变量，如下所示：

Employee(Department department,String name, int age)
{
    this.department = department;
    this.name = name;
    this.age = age;
    this.checks = new PrimeAgeChecker(this);
}

此外，正如Christian所提到的，将

PrimeAgeChecker

传递给

GetChecker

您的方法是没有意义的：

public PrimeAgeChecker GetChecker(PrimeAgeChecker checks){
    return checks;
}

没有意义，因为它只是重新调整给定的值。此外，您从未实例化名为

checks

的实例变量。在代码的后面，当您调用

GetChecker（checks）

时，由于该变量从未被实例化，所以您将传递null，然后返回null

如果您说它应该返回

true

或

false

值，那么您需要：

将

GetChecker

的返回类型设置为

boolean

，并从方法签名中删除

checks

参数。请记住，由于

GetChecker

方法是一个实例方法，并且

checks

字段也是同一对象的实例成员，因此不需要将参数传递给该方法；该方法可以直接调用它

实例化

检查

成员变量（最可能在构造函数中）

考虑到PrimeAgeChecker类的功能，我猜您打算调用

返回checks.check（）

还有一些小建议，您有两个拼写错误/命名约定错误：

• 我猜，您的

  emplo

  变量应该被命名为

  employees

  或类似的名称。getter和setter方法应该类似地重命名
• 与Java标准一样，

  GetChecker

  方法的第一个字母应该小写。这不会导致任何语法问题，因为Java并不关心，但它是这种语言的标准，如果代码一致，它会使您的代码更容易被其他人（以及您自己）阅读

---

现在，我如何对部门和员工姓名进行排序？你有什么想法让我从开始吗？@fransraharja

public PrimeAgeChecker GetChecker(PrimeAgeChecker checks){
    return checks;
}