在Null对象中调用非静态方法JAVA？

Question

**public void testCompareTo() {
    System.out.println("compareTo");
    Patient p = null;
    Patient instance = null;
    int expResult = 0;
    int result = instance.compareTo(p);
    assertEquals(expResult, result);
}**

Is there a way to call a method in a null object or do I have to do an Exception here?

Answer 1

No, you can't call a non-static method on a null object, since that would cause a NullPointerException .

You must verify that instance is not null before calling instance.compareTo(p) .

Answer 2

null objects by definition are... nothing. You can't invoke an instance level method on a null object without causing a NullPointerException .

Answer 3

在这种情况下，NullPointerException是不可避免的，因为Java无法从null对象获取任何引用，这使得抛出NullPointerException很明显