Thread: Help with Inheritance in Java.

hey i was leaning inheritance and tried to implement it in Java.This is my base class vehicl.java

public class vehicle{
	private int topSpeed;
	private int cubicCap;
	private String modelName;
	private boolean hasAlloy;
 
	public void vehicle(int topSpeed,int cubicCap,String modelName,boolean hasAlloy){
		this.topSpeed=topSpeed;
		this.cubicCap=cubicCap;
		this.modelName=modelName;
		this.hasAlloy=hasAlloy;
		}
 
	public void getInfo(){
		System.out.print("The car model is "+modelName+" and the Top Speed is "+topSpeed+
						 "\nCapacity : "+cubicCap+"Alloy :"+hasAlloy+".");
					}
 
	}

I also have a derived class called car.java.What i wanted to do in the derived class was that i wanted to override the constructor as well as the getInfo() method from the base class.I wanted to add an additional attribute to the car "numberSeats" and display tat too when the object to car class calls the getInfo() method .It showed an error "identifier required" when i tried to compile car.java program.

import java.util.Scanner;
public class car extends vehicle{
	//int numberSeats;
	//System.out.println("Enter the number of Seats");
	Scanner numberSeats=new Scanner(System.in);
	numberSeats=numberSeats.nextInt();
	//System.out.println(numberSeats.nextInt());
 
	public void car(int numberSeats){
		this.numberSeats=numberSeats;
		}
 
	public void getInfo(){
		System.out.print("The car model is "+modelName+" and the Top Speed is "+topSpeed+
						 "\nCapacity : "+cubicCap+"Alloy :"+hasAlloy+".\n"+
						 "Seating Capacity :"+this.numberSeats);
					}
		}

The main program Inheritance.java also threw a few errors .

public class Inheritence{
	public static void main(String []args){
		vehicle objectVehicle=new vehicle(500,1000,"polo",false);//Shows error that it requires no formal arguments.
		objectVehicle.vehicle(250,1000,"vento",true);//Works fine
		objectVehicle.getInfo();
		//car objectCar=new car();
		//objectCar.getinfo();
		}
	}

Could you explain the errors that i get when i tried to compile car.java without using super keyword or without defining the constructor from the Car class ?

I'll keep the naming convention in mind the next time

The errors from car.java
D:\java>javac car.java
car.java:4: error: <identifier> expected
System.out.println("Enter the number of Seats");
^
car.java:4: error: illegal start of type
System.out.println("Enter the number of Seats");
^
car.java:6: error: <identifier> expected
numberSeats=numberSeats.nextInt();

Errors in Inheritance.java
D:\java>javac inheritance.java
inheritance.java:3: error: constructor vehicle in class vehicle cannot be applie
d to given types;
vehicle objectVehicle=new vehicle(500,1000,"polo",false);//Shows
error that it requires no formal arguments.
^
required: no arguments
found: int,int,String,boolean
reason: actual and formal argument lists differ in length
inheritance.java:7: error: cannot find symbol
objectCar.getinfo();
^
symbol: method getinfo()
location: variable objectCar of type car
2 errors

Thanks a lot.Is it mandatory for all the executable statements to be inside a constructor or method ? unlike in C/C++ ? I did put all the executable statements inside the constructor for car class.

import java.util.Scanner;
public class car extends vehicle{
 
	public void car(){
		System.out.println("Enter the number of Seats");
		Scanner numberSeats=new Scanner(System.in);
		this.numberSeats=numberSeats.nextInt();
		}
 
	public void getInfo(){
		System.out.print("The car model is "+modelName+" and the Top Speed is "+topSpeed+
						 "\nCapacity : "+cubicCap+"Alloy :"+hasAlloy+".\n"+
						 "Seating Capacity :"+this.numberSeats);
					}
		}

Still there was two errors
D:\java>javac car.java
car.java:7: error: cannot find symbol
this.numberSeats=numberSeats.nextInt();
^
symbol: variable numberSeats
car.java:13: error: cannot find symbol
"Seating Capacity :"+this.numbe
rSeats);
^
symbol: variable numberSeats
2 errors

D:\java>javac car.java
car.java:7: error: cannot find symbol this.numberSeats=numberSeats.nextInt();
^
symbol: variable numberSeats
car.java:13: error: cannot find symbol "Seating Capacity :"+this.numberSeats);
^
symbol: variable numberSeats
2 errors