如何从静态方法返回非静态变量？

Question

Even through these reference Tri1 , I am not able to return base value.

public class Triangle {

    private double base;

    Triangle Tri1 = new Triangle();

    public static double getBase() 
    { 
        return Tri1.base; 
    }
}

Answer 1

You can make Tri1 a static variable:

public class Triangle {

private double base;

static Triangle Tri1 = new Triangle();

public static double getBase() 
  { 
    return Tri1.base; 
  }
}

Or make getBase instance method:

public class Triangle {

private double base;

Triangle Tri1 = new Triangle();

public double getBase() 
  { 
    return Tri1.base; 
  }
}

You can not return instance variable from static method.

Answer 2

You try to call the private member of a specific object. To access base, you would have to make it static. But then every triangle has the same base value.

Answer 3

public class Triangle {

  private double base;

  static Triangle Tri1 = new Triangle();

  public static double getBase() 
  { 
    return Tri1.base; 
  }
}

Please make above changes. It runs without error. Please remember, from static methods, we have access only static members of that class, be it a static variable or another static method. Static methods are loaded into memory before the non-static members get loaded..so any access of non-static members from static methods looks like you are going to access something that is not created .so you get a compilation error.