Java中的静态方法可以调用非静态方法

Question

有人说在Java中我们不能从静态方法中调用非静态方法。这到底意味着什么？我们总是可以使用对象调用非静态方法frm static。

Answer 1

Here is a nice code piece to illustrate what it means:

class MyClass{

    static void func1(){
        func2(); //This will be an error
    }

    void func2(){
        System.out.println("Hello World!");
    }

}

Answer 2

To call a non-static method, you need an instance (object) - because these methods belong to an instance, and in general only make sense in the context of an instance.

Static methods don't belong to an instance - they belong to the class. So there is no need to create an instance first, you can just call MyClass.doSomething()

void foo(){
  MyClass.doSomething();
}

But you can call a non-static method from a static method provided you first create an instance .

static void bar(){
  MyObject o = new MyObject();
  o.doSomething();
}