Polymorphism

Polymorphism

When methods understand the same message but it means different things, so, if we have two classes and both classes have a method called toString()

Each classes toString() will do something slightly different.

When methods are overridden we can say that they are Polymorphic

Formal Argument v Actual Argument

Formal Argument...

Formal when declaring and the Actual is when called.

public doSomething (Frog aFrog) //Formal

dosomething(jimmy) // Actual

call a non static method from within a static method

To call a non static method from within a static method, do as below;

Exceptions in Java

ArithmeticException – an instance of this class is thrown when an exceptional arithmetic condition has occurred; for example, when integer division by zero has occurred.

NullPointerException – an instance of this class is thrown when you try to send a message to a reference variable whose value is null; that is, it does not reference an object. (The use of the word ‘pointer’ rather than ‘reference’ is a curiosity of the language, a throwback to C language terminology.)

NumberFormatException – an instance of this class is thrown to indicate that a method that converts a string to one of the numeric types has been passed an argument that does not have the appropriate format.

IndexOutOfBoundsException – an instance of this class is thrown when a program tries to access a string with an index outside the valid limits.

public static final

public static final

public static final int HOURS_IN_DAY = 24;

Java Method Overriding

Declaring a method in subclass which is already present in parent class is known as method overriding.

Java Method Overloading

Method Overloading is a feature that allows a class to have two or more methods having same name but ONLY if their argument lists are different.

namespace std C++

Use of namespace std as below;

#include<iostream>

using namespace std;

int main()
{
cout<<("Hello there...")<<endl;
return 0;
}

Compile C/C++ in Linux

gcc source.c -o executable.o

OR

g++ source.c -o executable.o

chmod +x executable.o
./executable.o

C++ Note on Declarations

In C++ we must declare a Function/Routine before we use it UNLESS it appears in code before it is first used.