线程“main”java中出现异常。lang.NullPointerException:无法读取数组长度，因为“”为null[重复]

Question

我有这个主代码

    public static void main(String[] args)
    {
        //display Gui
        DisplayGUI();
        //input Person
        InputPerson();
        //display input data
        Display();
        //sort person
        //SortbySalary();
        //display sorted person
        //Display();        
        
    }

    private static void DisplayGUI() {
        System.out.println("=====Management person Programmer=====");
    }
    
    private static void InputPerson() {
        //array of person
        Person persons[] = new Person[3];
        //constructor
        Person person = new Person();
        
        for(int i = 0; i<3; i++){
            persons[i] = person.InputPersonInfo(person.getName(),person.getAddress(),person.getSalary());
        }
        
        for (Person p: persons){
            person.DisplayPersonInfo(p);
            System.out.println();
        }        
    }

    public static void Display() {
        Person person = new Person();
        Person persons[] = null;
                for (Person p: persons){
            person.DisplayPersonInfo(p);
            System.out.println();
        } 
    }
}

这是我的个人课

class Person {
    private String name;
    private String address;
    private double salary;

    public Person() {
    }

    public Person(String name, String address, double salary) {
        this.name = name;
        this.address = address;
        this.salary = salary;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }
    
    public Person InputPersonInfo(String name, String address, double salary){
        Scanner sc = new Scanner(System.in);
        System.out.println("Input Information of person:");
        System.out.println("Please input name:");
        name = sc.nextLine();
        System.out.println("Please input Address)");
        address = sc.nextLine();
        System.out.println("Please input salary:");
        salary = sc.nextDouble();
        
        return new Person(name,address,salary);
        
    }
    public void DisplayPersonInfo(Person persons){
        System.out.println("Information of Person you entered");
        System.out.println("Name:" + persons.getName());
        System.out.println("address:" + persons.getAddress());        
        System.out.println("slary:" + persons.getSalary());        
    }

我不明白当我在InputPerson（）类中推送这段代码时，它会显示我输入的人的信息

        for (Person p: persons){
            person.DisplayPersonInfo(p);
            System.out.println();
        } 

但当我在Display（）类中尝试这样做时，它总是告诉我错误“无法读取数组长度，因为”“为null”

我不知道如何将我在InPutPerson（）类中输入的数据传递到Display（）类，请帮助我

Answer 1

InputPerson方法应返回persons，然后将此输出用作display（persons）方法中的参数。

比如：

    public static void main(String[] args) {
        //input Person
        Person persons[] = InputPerson();
        //display input data
        display(persons);

    }

    private static Person[] InputPerson() {
        Person persons[] = new Person[3];
        Person person = new Person();

        for (int i = 0; i < 3; i++) {
            persons[i] = person.InputPersonInfo(person.getName(), person.getAddress(), person.getSalary());
        }

        for (Person p : persons) {
            person.displayPersonInfo(p);
            System.out.println();
        }
        return persons;
    }

    public static void display(Person[] persons) {
        Person person = new Person();
        for (Person p : persons) {
            person.displayPersonInfo(p);
            System.out.println();
        }
    }
}