What is Setter Methods explain with an example?

Setter methods, also called as mutator methods, merely set the value of a field to a value specified through the argument to the method. These methods almost always return void.

One general idiom in setter methods is to use this.name to refer to the field and provide the argument the similar name as the field. For example,
class Car {

String licensePlate; // e.g. "New York A456 324"
double speed; // kilometers per hour
double maxSpeed; // kilometers per hour

// setter method for the license plate property
void setLicensePlate(String licensePlate) {
this.licensePlate = licensePlate;
}

// setter method for the maxSpeed property
void setMaximumSpeed(double maxSpeed) {
if (maxSpeed > 0) this.maxSpeed = maxSpeed;
else this.maxSpeed = 0.0;
}

// accelerate to maximum speed
// put the pedal to the metal
void floorIt() {
this.speed = this.maxSpeed;
}

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;
}
}
}