java, get set methods

问题

This question has been asked before, but even after reading:

Java "Get" and "Set" Methods

Java Get/Set method returns null

And more I still don't understand how to solve my problem.

When accessing variables in a class using get methods from another class I receive the value null.

How do I recieve my correct values instead of null?

---

This is the class where I try to get my variables FROM (not everything included).

public class RLS_character_panel extends javax.swing.JPanel implements ActionListener, ItemListener { 

    private String name1 = "hello"; 

    public String getName1() { 
        return name1; 
    } 

    public void setName1(String name1) { 
        this.name1 = name1; 
    } 

} 

---

This is the class where i try to get the values TO. This class extends JFrame so that I can add a JPanel which displays the variable. (the JPanel is yet another class called: RLS_strid_panel , which is added upon this frame).

public class RLS_strid_java extends JFrame { 

    RLS_character_panel test = new RLS_character_panel(); 

    String name1 = test.getName1(); 

    RLS_strid_panel p = new RLS_strid_panel(namn1); 

    // constructor
    public RLS_strid_java(String titel) { 
        super(titel); 
        this.setSize(1000, 772); 
        this.setVisible(true); 
        this.setResizable(false); 
        this.add(p); 
    } 
}

---

the Jpanel Displays null.

回答1:

To understand get and set, it's all related to how variables are passed between different classes.

The get method is used to obtain or retrieve a particular variable value from a class.

A set value is used to store the variables.

The whole point of the get and set is to retrieve and store the data values accordingly.

What I did in this old project was I had a User class with my get and set methods that I used in my Server class.

The User class's get set methods:

public int getuserID()
    {
        //getting the userID variable instance
        return userID;
    }
    public String getfirstName()
    {
        //getting the firstName variable instance
        return firstName;
    }
    public String getlastName()
    {
        //getting the lastName variable instance
        return lastName;
    }
    public int getage()
    {
        //getting the age variable instance
        return age;
    }

    public void setuserID(int userID)
    {
        //setting the userID variable value
        this.userID = userID;
    }
    public void setfirstName(String firstName)
    {
        //setting the firstName variable text
        this.firstName = firstName;
    }
    public void setlastName(String lastName)
    {
        //setting the lastName variable text
        this.lastName = lastName;
    }
    public void setage(int age)
    {
        //setting the age variable value
        this.age = age;
    }
}

Then this was implemented in the run() method in my Server class as follows:

//creates user object
                User use = new User(userID, firstName, lastName, age);
                //Mutator methods to set user objects
                use.setuserID(userID);
                use.setlastName(lastName);
                use.setfirstName(firstName);               
                use.setage(age); 

回答2:

your panel class don't have a constructor that accepts a string

try change

RLS_strid_panel p = new RLS_strid_panel(namn1);

to

RLS_strid_panel p = new RLS_strid_panel();
p.setName1(name1);

来源：https://stackoverflow.com/questions/36102768/java-get-set-methods