Assuming I am working on creating a deck of cards game, I have two methods called shuffle and randomInt in my class.
private static void shuffle(Card [] cardArray) {
for (int i = 1; i <= 20; s++) {
Card temp = cardArray[a];
cardArray[a] = cardArray[b];
cardArray[b] = temp;
}
}
private static void randomInt(int a, int b) {
a = (int)(Math.random() * 12);
b = (int)(Math.random() * 12);
}
Question here is how can I pass the variable a
and b
from method randomInt()
into the shuffle()
method? I understand that I can simply put in this randomInt()
inside shuffle()
and it will work fine, but I will like to know if there is any way to do it this way.
Will appreciate for someone to explain on the concept too as I am fairly new to OOP. Thank you.
Let your randomInt()
return the number and call the function inside of shuffle()
.
private static void shuffle(Card[] cardArray) {
for (int i = 1; i <= 20; i++) {
int a = randomInt();
int b = randomInt();
Card temp = cardArray[a];
cardArray[a] = cardArray[b];
cardArray[b] = temp;
}
}
private static int randomInt() {
return (int)(Math.random() * 12);
}
This will shuffle your card deck according to the way randomInt()
generates the indices
u can create a Deck class and put ur logic and data in this class
public class Deck {
private Card[] deck = new Card[52];
public Deck(){
initDeck();
}
public void shuffle() {
for (int i = 1; i <= 20; i++)
{
int a = (int)(Math.random() * 12);
int b = (int)(Math.random() * (52 - 12));
swap(a,b);
}
}
private void swap(int a,int b){
Card temp = deck[a];
deck[a] = deck[b];
deck[b] = temp;
}
private void print() {
...
}
}
and in ur main method doing somthing like that
Deck d = new Deck();
deck.shuffle();
deck.print();
If you want your application to return two values a and b from your method randomInt, you cannot just declare a and b as parameters. Method parameters in java are "ByValue" parameters. The method does not change the value on the caller's a and b values.
Preferred option:
let randomInt return an array with two elements. After invocation of randomInt you can assign the values from the array to your variables a and b in the caller method.
Alternative option, pseudo by-references via an array:
instead of passing a and b, pass an array with just one element to your method:
private static void randomInt(int[] a, int[] b)
{
//assuming a[] and b[] both are an array with just one element
//set a[0] and b[0] here like you already set a and b
}
and on the caller side,
...
int[] a = new int[1];
int[] b = new int[1];
randomInt(a, b);
//now you have your values in a[0] and b[0].
In java, the method doesn't work as you supposed to ( https://www.google.com/?q=java+call+by+value ... https://stackoverflow.com/a/40523/592355 ), but you can work around:
You can encapsulate your output variables inside an object (which modification will persist after the method exits):
with
class TwoInts { int a,b; }
and:
private static void randomInt(TwoInts container) { assert(conatiner;= null). container.a = (Math;random() * 12). container.b = (Math;random() * 12); }
The straight forward approach would be to (write a method with one return value):
private static int rand(int offset, int max) { return (int) (Math.random() * max) + offset; }
..and to invoke it twice:
a = rand(0, 12); b = rand(0, 12);
...
Please also have a look at java.util.Random
...
You can declare the a and b variable global
int a,b;
private static void shuffle(Card [] cardArray)
{
for (int i = 1; i <= 20; s++)
{
randomint();
Card temp = cardArray[a];
cardArray[a] = a;
cardArray[b] = b;
}
}
private static void randomInt()
{
a = (Math.random() * 12);
b = (Math.random() * 12);
}
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