Question

有人可以解释一下变量在Java开始时做什么吗？我对我为我的计算机类所做的代码中的变量指出的内容感到困惑。我太新了，甚至不知道要搜索什么来得到正确的答案，而我正在使用的书并没有帮助解释任何事情，因为它将所有变量命名为相同的，这使我对从哪里调用的内容感到困惑。谢谢乍得

public void setEmpID(int NewID)将this.empID设置为NewID？

// access modifier is set to public and a class is declared and named Employee
public class Employee  
{   
    private int empID; 
    private String firstName; 
    private String lastName; 
    private double monthlySalary; (Are these to store the variable values from the main method until class creation or are they defining variables in the object that will be created?)

    //Constructor intializes class Employee to create object Employee with instance variables above. Must be same name as class

    **public Employee(int empID, String firstName, String lastName, double newSalary) //(is this the storage until the class is created or the defining of the variables for the object that will be created?)**
    {
        //ensures empID is a positive number before assignment
        if (empID > 0.0) 
            //assigns empID to variable "empID"
            **this.empID = empID; //where does this assign empID? in the new object or in this class temporarily until the object is created?**

        //assigns firstName to variable "firstName"
        this.firstName = firstName; 

        // assigns lastName to variable "lastName"
        this.lastName = lastName;                         

        //ensure monthlySalary is a positive number before assignmentand if 
        //ends constructor
    }

    **//method that sets the empID(where are these set?)**
    public void setEmpID(int newID)
    {
        this.empID = newID;
    }

    //method that sets the firstName
    public void setFirstName(String newFirst)
    {
        this.firstName = newFirst;
    }

     //method that sets the lastName
    public void setLastName(String newLast)
    {
        this.lastName = newLast;
    }

    //method that sets the monthlySalary for the new obj
    public void setMonthlySalary(double newSalary)

    {
        this.monthlySalary = newSalary;
    }

    **//Gets empid from the object and returns empID to the calling method (I think this is right)**
    public int getEmpID()
    {
        return empID;
    }  

    //gets first name from the object and returns first name to the calling method  
    public String getFirstName()
    {
        return firstName;
    }  

    //gets last name from the object and returns last name to the calling method  
    public String getLastName()
    {
        return lastName;
    }  

    //gets monthly salary from the object and returns it to the calling method  
    public double getMonthlySalary()
    {
        return monthlySalary;          
    }

}

Answer 1

如果您想了解变量可见性，这可能有所帮助。 SO Question

至于变量具有相同名称时，请参阅下面的代码

<强> Example.java

public class Example {
    private int empID = 0; //Creates a global variable

    public Example(int empID) { //Creates a local variable that is 
                                //initiated when contructor is called
        this.empID = empID; //Calls the global variable and sets it
                            //equal to the local variable
        exampleMethod(); //Calls the method below
    }

    private void exampleMethod() {
        empID = 1; //Sets the global variable to = 1
        //This is the same as this.empID = 1;
    }

    public void setEmpID(int newID) {
        empID = newID; //Sets the global variable to = newID
        //This is the same as this.empID = newID;
    }

    public int getEmpID() {
        return empID; //Gets the value of the global variable
                      //empID. Example use below
    }
}

<强> Example2.java

public class Example2 {
    public Example2() {
        Example ex = new Example(1); //Create and initate an Example class
        System.out.println(ex.getEmpID()); //Prints out Example.empID, aka 1
        ex.setEmpID(2);
        System.out.println(ex.getEmpID()); //Prints out Example.empID, aka 2
    }

    public static void main(String[] args) {
        new Example2(); //Creates and initates an Example2 class
    }
}

至于变量类型，这个简短的教程将介绍它们。 Tutorial

我无法弄清楚变量调用的位置或来源

1 个答案: