Write program to Passing Arguments to Methods ?

It's generally considered bad form to access fields directly. Instead it is considered outstanding object oriented practice to access the fields only by methods. This allow you to change the implementation of a class without changing its interface. This also allow you to enforce constraints on the values of the fields.

To do this you need to be able to send information into the Car class. This is completed through passing arguments. For example, to permit other objects to change the value of the speed field in a Car object, the Car class could gives an accelerate() method. This method does not permit the car to exceed its maximum speed, or to go slower than 0 kph.

void accelerate(double deltaV) {

this.speed = this.speed + deltaV;
if (this.speed > this.maxSpeed) {
this.speed = this.maxSpeed;
}
if (this.speed < 0.0) {
this.speed = 0.0;
}

}
The first line of the method is called as its signature. The signature
void accelerate(double deltaV)
indicates in that accelerate() returns no value and takes a single argument, a double that will be referred to as deltaV inside the method.

deltaV is a purely formal argument.
Java passes method arguments by value, not by reference.