使用其他类的方法

Question

The difference between (a) import somePackage.someClass; and (b) someClass object = new someClass(); is that (a) will allow call the methods from the imported class without creating new instances of it, while (b) will create an object using the template class and therefore the methods for the class someClass will belong to the object object . So if I want to use a method someMethod() from someClass in (b) I'd call it through the object object. Is it how it works?

Answer 1

• Yes you can use static methods from a class directly
• Yes you can use methods from a class by creating an object

But more important thing than just the above options available is when to use which. First type of call is to class methods whereas the second class is to instance methods.

Instance Methods vs Class Methods: Each class represents a set of attributes and behaviour. Instance methods usually represent the behaviour. example if Person is a class and Robb is an object, then robb.weight can be attribute, robb.write() would be an instance method and Person.type() (ans: species) or Person.population (ans: total number of instances) can be class methods.

Also you represent instance methods in textual writing as ClassName#instanceMethod and ClassName.classMethods

Answer 2

No, you are wrong

Simplistically if the class that you want to use is not in the same package then you need to import it, or fully path the class eg java.util.ArrayList .

If the methods are not static, then you will need to create a new Instance of the class you want to use.

Answer 3

You can use methods from other class directly only if it is a static method. You will also have to add static in your import statement if you want to use the method name directly without prefixing it will the class name. For non-static methods you have to create instance of the class and then call that method.