Object-Oriented Programming Lab 1 Exercises Introduction Today's ...

Introduction

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Object-Oriented Programming Lab 1 Exercises

Who’s who Ewan Klein

Scheduled vs. drop-in labs

School of Informatics

Inf1 :: 2009/10

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Object-Oriented ProgrammingLab 1 Exercises

Inf1 :: 2009/10

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Today’s Exercises

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Already discussed in this week’s lecture.

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HelloWorld

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PersonalGreeting

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Adder

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HelloWorld

Variants:

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Divider

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modify the string that is being printed out experiment with print vs. println make some deliberate errors to see what happens (e.g., miss out a closing }), mis-spell the class name, use single quotes for the string)

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Object-Oriented ProgrammingLab 1 Exercises

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HelloWorld

PersonalGreeting

Already discussed in this week’s lecture. Variants:

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New stuff — uses variables and functions

modify the string that is being printed out experiment with print vs. println make some deliberate errors to see what happens (e.g., miss out a closing }), mis-spell the class name, use single quotes for the string)

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Object-Oriented ProgrammingLab 1 Exercises

Inf1 :: 2009/10

Let’s look at variables

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Declaring Variables

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Putting it Together

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Declarations plus Assignment

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But Java wants to know the type of the value!

String name;

Declaring a variable: type var;

name = ”Bob”;

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String name;

int number; number = 33;

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int number;

Important: first declare the variable (reserve some space in memory); then assign a value of the appropriate type.

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String name = ”Bob”; int number = 33;

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Object-Oriented ProgrammingLab 1 Exercises

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Object-Oriented ProgrammingLab 1 Exercises

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Hello World with added variables

Using return value from a function

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Putting the message in a variable

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public class HelloWorld {

Suppose we have a function today() that returns a string giving today’s date. We can assign this return value to a variable:

public static void main ( String [] args ) {

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String msg = ”Hello World!”;

Assigning a return value . ..

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Finally

Adder and Divider should be fairly self-explanatory

Questions? The lab 1 exercises: http://www.inf.ed.ac.uk/teaching/courses/inf1/oop/Labs/build/ html/lab1.html

Or follow link from: http://www.inf.ed.ac.uk/teaching/courses/inf1/oop/

Ewan Klein (School of Informatics)

Object-Oriented ProgrammingLab 1 Exercises

Inf1 :: 2009/10

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String date = today();

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System.out.println( msg ); }

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