Java - External Classes

7/30/2019 Java - External Classes

1/12

Java

Scanner ClassKeyboard Class


2/12

User Interaction

So far when we created a programthere was no human interaction

Our programs just simply showed one

output

In order for users to interact with our

programs we need to use external

classes


3/12

External Classes

External classes are ready madeclasses that are used to allow users to

interact with a program

Two examples of external classes are;

1. The Scanner Class

2. The Keyboard Class


4/12

Using External Classes

In order to use external classes youwould need to let your program know

that you would like to use them

In order to call ALL external classes

you need to use the following code

snippet

import java.util.*;


5/12

Scanner & Keyboard Class

The scanner and keyboard classesare both used to allow users to

interact with the program

They are used to ask users for an

input

The input is normally done using the

actual keyboard


6/12

Scanner Class

The first thing you need to do is createan instance of the Scanner class

Class Creates aninstance of

the class

Name

Constructor


7/12

Scanner Inputs

You could input many different datatypes;

Data Type Method

String String str = s.next();

double double d = s.nextDouble();

long long l = s.nextLong();

short short sh = s.nextShort();

byte byte b = s.nextByte();

float float f = s.nextFloat();

boolean boolean bo = s.nextBoolean();

t t


8/12

Examples

mport ava.ut . canner;

class test {public static void main (String args[]){

//Create an instance of the ScannerScanner s = new Scanner(System.in);

System.out.print("Enter your name : ");//Since the name is a String the String

//has to be usedString name = s.next();

System.out.println("How old are you ? ");//The age can be stored in a longlong age = s.nextLong();

System.out.println("You are "+name+" and you are "+age+"years old.");

}

}


9/12

Keyboard Class

This class is also used to let usersinput data from the keyboard

The user can input the same datatypes we spoke about when we used

the scanner class


10/12

Using the Keyboard Class

Data Type Method

int Keyboard.readInt();

byte Keyboard.readByte();

short Keyboard.readShort();

long Keyboard.readLong();

float Keyboard.readFloat();

double Keyboard.readDouble();

char Keyboard.readChar();

boolean Keyboard.readBoolean();

Keyboard.readString();


11/12

class test {public static void main (String args[]){

System.out.print("Enter your name : ");String name = Keyboard.readString();

System.out.println("How old are you ? ");long age = Keyboard.readLong();

System.out.println("You are "+name+" andyou are "+age+" years old.");

}}


12/12

Which is better to

use?Why?

Documents

Java - External Classes