Passing an argument to a class in Java

Question

Let's say I have a class and I want one of its methods to behave differently depending on an argument. What I want to do is something like this (I know this doesn't work in Java):

class myClass(int a) {
    public void myMethod() {
        if (a == 1)
            // do something
        if (a == 2)
            // do something else
    }
}

Is there a way to do this?

Answer 1

You have two ways to do that.

• Pass the argument to the class contructor, and keep a local reference to it. You can then use it in all the methods of your class.

Like this:

class MyClass {
    private final int a;

    public MyClass(int a) {
        this.a = a;
    }

    public void myMethod() {
        if (a == 1)
            // do something
        if (a == 2)
            // do something else
    }
}

• Pass the argument to the method, if you intend to use it only in that method.

Like that:

class MyClass {
    public void myMethod(int a) {
        if (a == 1)
            // do something
        if (a == 2)
            // do something else
    }
}  

Answer 2

The argument must be passed to the method, not to the class:

class MyClass { // note that class names should start with an uppercase letter.
    public void myMethod(int a) {
        if (a == 1)
            // do something
        if (a == 2)
            // do something else
    }
}

Read the Java language tutorial .

Answer 3

You can pass this argument in constructor

class MyClass {
    private int a;
    public MyClass(int a){
        this.a = a;
    }
    public void myMethod() {
        if (a == 1)
            // do something
        if (a == 2)
            // do something else
    }
}

Answer 4

Polymorphism is the way to go. Define your base class first with an abstract method myMethod() and then extend it with two classes providing two different implementations of the method.