关于Java的一些基本问题

Question

I am new to Java. I know the basics and i have 2 questions that if they are answered they will really help me in programming. Here's my code:

package RollPack;

import java.util.Random;

public class RollClass {
     static int result;

    public static void main(String[] args){

        DerpRandom();


    }
    static void DerpRandom(){
        Random rand = new Random();
        result = rand.nextInt(7);
        System.out.println("You rolled a: "+result);
        DerpResult(result);
    }
    static void DerpResult(int result){
        if (result < 7){
            System.out.println("Yeh, it works..");
        }
    }
}

My questions:

1. What does DerpRandom(); mean in words?
2. What does DerpResult(result); mean in words?

I mean, by writing DerpResult(result) , does it mean that it adds result to DerpResult? What does it mean?

Answer 1

In words:

DerpRandom(); = "Call the method named DerpRandom which has no parameters, and is in the current class".

DerpResult(result); = "Call the method named DerpResult that takes one parameter assignment-compatible with int , and is in the current class, and pass it the value of result as an argument".

When I say "in the current class" I mean "defined in the current class, or defined in one of its superclasses and accessible from the current class".

Answer 2

DerpRandom is a poorly named method which generates a random result between 0 and 6. DerpResult is a poorly named method which takes a parameter and ensures that the result comes in below 7.

No state is changed between the two methods. DerpResult is only checking the value of DerpRandom .

Answer 3

DerpRandom() means i have a function that i will call that takes no input and does some execution. it returns nothing because its void

DerpRandom(result) means I have a function that takes an input of an integer called result and does something but returns nothing due to the void return type.

What does the code do ?

derpRandom() prints a number from 0-6 then it calls DerpResult(result);

derpResult(result) makes sure the number passed into it is less than 7 which it is when the other method called it.

so you could call DerpResult(result); there which is the same as calling DerpResult(6);

however you could also call DerpResult and change the input param, say DerpResult(1) which would yield the same thing or DerpResult(11) which wouldnt print anything.

Answer 4

DerpRandom and DerpResult both are class methods. By using the static keyword. Which means these methods are created only one copy per class.

DerpRandom is the caller method and DerpResult is the callee.

DerpRandom randomly selects random number, then prints the result with a message, and DerpResult method is called with a primitive type of int variable named result passed by argument. Which means the argument passed to DerpResult method is a duplicate copy. If for example the result was defined outside before the DerpResult is called and changed inside the method the change won't reflect after the DerpResult is called.

The DerpResult method checks if the result is below 7 or not. If it is it prints "Yeh, it works.." Both of these methods has default access modifier or package access modifier which means the class where it is defined and all the java source code files in the same package can access these two methods.

Both of these methods don't return anything. That's the reason why the void keyword is used.

I mean, by writing DerpResult(result), does it mean that it adds result to DerpResult? What does it mean?

No. It doesn't add anything. DerpResult() method just compares the variable result with 7 to check if it is less than 7 or not. If it is, it prints a message and if it is not it exits the method. That's all.