Introduction to Java - Input, Program Control and Instantiation

1
Introduction to Java - Input,
Program Control and Instantiation
Department of Computer and Information
Science,School of Science, IUPUI
Dale Roberts, Lecturer Computer Science,
IUPUI E-mail droberts_at_cs.iupui.edu
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2.5 Another Java Application Adding Integers

• Upcoming program
• Use Scanner to read two integers from user
• Use printf to display sum of the two values
• Use packages

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Outline

• nextInt

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Outline
Read an integer from the user and assign it to
number2.
Calculate the sum of the variables number1 and
number2, assign result to sum.

• Addition.java
• (2 of 2)
• 4. Addition
• 5. printf

Display the sum using formatted output.
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2.8 Decision Making Equality and Relational
Operators

• Condition
• Expression can be either true or false
• if statement
• Simple version in this section, more detail later
• If a condition is true, then the body of the if
  statement executed
• Control always resumes after the if statement
• Conditions in if statements can be formed using
  equality or relational operators (next slide)

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Fig. 2.14 Equality and relational operators.
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Outline

• Comparison.java
• (1 of 2)
• 1. Class Comparison1.1 main1.2
  Declarations1.3 Input data (nextInt)1.4
  Compare two inputs using if statements

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Outline

• Comparison.java
• (2 of 2)
• Program output

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Declaring a Class with a Method and Instantiating
an Object of a Class

• Each class declaration that begins with keyword
  public must be stored in a file that has the same
  name as the class and ends with the .java
  file-name extension.

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Outline

• GradeBook.java

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Outline

• GradeBookTest.java

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Compiling an Application with Multiple Classes

• Compiling multiple classes
• List each .java file in the compilation command
  and separate them with spaces
• Compile with .java to compile all .java files in
  that directory

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Notes on Import Declarations

• java.lang is implicitly imported into every
  program
• Default package
• Contains classes compiled in the same directory
• Implicitly imported into source code of other
  files in directory
• Imports unnecessary if fully-qualified names are
  used

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Acknowledgements

• http//java.sun.com/docs/books/tutorial/getStarted
  /TOC.html
• Pearson Education, Lewis and Loftus.
• Deitel, Java How to Program
• http//www.cs.wustl.edu/plezbert/contcom/thesis/n
  ode6.html
• http//www.cs.usfca.edu/parrt/course/652/lectures
  -Spring-2004/language.impl.overview.pdf
• http//ei.cs.vt.edu/history/Youmans.Java.html