Java 如何使用显示方法并调用构造函数？
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How do I use display method and call constructor?
提问by New2Java
I'm required to use a variable for x and y. I must set up a method to get x, y. I must use a method to set x and y. I must use a display method to display the points of x and y. Then use a constructor that accepts user input and sets them to x and y. Finally create a main class that creates 2 instances of x and y. I think my problem is occurring my display method. My program compiles/builds with no errors; however nothing displays or prompts user for input. Do I possibly need to call my constructor in the first class before trying to call the first class in the main method?
我需要为 x 和 y 使用一个变量。我必须设置一个方法来获取 x, y。我必须使用一种方法来设置 x 和 y。我必须使用显示方法来显示 x 和 y 的点。然后使用接受用户输入并将它们设置为 x 和 y 的构造函数。最后创建一个主类，创建 x 和 y 的 2 个实例。我认为我的问题出在我的显示方法上。我的程序编译/构建没有错误；但是没有任何显示或提示用户输入。在尝试调用 main 方法中的第一个类之前，我是否可能需要在第一个类中调用我的构造函数？
First File:
第一个文件：
public class Point2D extends JFrame
{
Scanner input = new Scanner(System.in);
private String x;
private String y;
public String getX()
{
return x;
}
public String getY()
{
return y;
}
public void setValue(String whatIsX, String whatIsY)
{
x = whatIsX;
y = whatIsY;
}
public void display()
{
System.out.println(x);
System.out.println(y);
}
public void Point2D()
{
System.out.println("Please enter value for X >>");
input.nextLine();
x = input.nextLine();
System.out.println("Please enter value for Y >>");
input.nextLine();
y = input.nextLine();
}
}
2nd File:
第二个文件：
public class MainPoint2D
{
public static void main(String[] args)
{
Point2D a = new Point2D();
Point2D b = new Point2D();
}
}
采纳答案by mdnghtblue
Remove voidfrom your "constructor":
void从“构造函数”中删除：
public Point2D()
{
System.out.println("Please enter value for X >>");
input.nextLine();
x = input.nextLine();
System.out.println("Please enter value for Y >>");
input.nextLine();
y = input.nextLine();
}
Constructors don't have return types, and the compiler is treating this as a class method.
构造函数没有返回类型，编译器将其视为类方法。
Also, don't forget to call any methods you want to execute after you create your object:
另外，不要忘记在创建对象后调用任何要执行的方法：
Point2D a = new Point2D();
Point2D b = new Point2D();
a.display();
b.display();
回答by outdev
Remove the voidin the public void Point2D()
删除无效的公共无效的Point2D（）
回答by Bill the Lizard
public void Point2D()defines a method named "Point2D" with a voidreturn type, not a constructor. Constructors don't have any return type, not even void. Change that to public Point2D().
public void Point2D()定义了一个名为“Point2D”的方法，带有void返回类型，而不是构造函数。构造函数没有任何返回类型，甚至void. 将其更改为public Point2D().
Currently, your mainmethod is calling the default Point2Dconstructor, which is not defined, so the compiler provides an empty one for you.
当前，您的main方法正在调用Point2D未定义的默认构造函数，因此编译器为您提供了一个空构造函数。
回答by ControlAltDel
I thik you want to change this
我想你想改变这个
public void Point2D()
{
System.out.println("Please enter value for X >>");
input.nextLine();
x = input.nextLine();
System.out.println("Please enter value for Y >>");
input.nextLine();
y = input.nextLine();
}
to this
对此
public Point2D()
{
System.out.println("Please enter value for X >>");
input.nextLine();
x = input.nextLine();
System.out.println("Please enter value for Y >>");
input.nextLine();
y = input.nextLine();
}
