242 ECE Spring 2003
Data Structures in Java
http://rio.ecs.umass.edu/ece242
Lecture 2
Prof. Lixin Gao
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Todays Topics
Introduction to Java Java Installation Simple Examples: HelloWorld.java Data Types Input/Output
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Why Java?
Object-Oriented Programming Language
Vs. C Like C++
Portable
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Object-Oriented Programming
Object-oriented programming vs. Function
Graphic user interface (GUI) Interactivity
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Portability of Java
Compiler Unix Compiler C source code MacOS Compiler Windows Compiler Binary code Unix MacOS Windows
Java source code
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Java Compiler
Byte Code
Java Virtual Machine (Interpreter)
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Applet Demo
Bookflip http://rio.ecs.umass.edu/ece242/applet/ bookflip/bookflip.html Lake http://rio.ecs.umass.edu /ece242/applet/lake/anlake2.html
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Installation
Install JDK 1.3.1 from http://java.sun.com/j2se/1.3/ first Install TextPad from http://www.textpad.com/download/index.html These software are available in computer lab
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Examples
HelloWorld.java
class HelloWorld {
public static void main(String args[]) {
System.out.println("Hello, World!");
}
}
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Compile/Run
Command for Compile Java
javac HelloWorld.java c:\jdk1.3.1_01\bin\javac HelloWorld.java
Command for Run Java
java HelloWorld c:\jdk1.3.1_01\bin\java HelloWorld
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Data Types (1)
Define a data type
Integer
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int i=100; short j; long red, green, blue; float height; double weight; boolean isover;
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Floating-Point Boolean
Data Types (2)
Char
char c=y;
String String message; String className=ece242;
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Expression
Add/Subtract
x = y + 3; m = n 4;
Multiply/division
x = y / 3; m=2*6;
More complex
z = (10+x)*5 +2*y;
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Expression
Type conversion (Be careful)
Examples: int x = 150; float y, z; y = x/60; z = (float)x/60; Result for y and z is different
y = 2; z = 2.5;
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Operations
from highest to lowest precedence
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. . ++ * + << < == & ^ && || ?: = [] -/ >> > != () ! % >>> <= ~
>=
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Examples
MinutesToHours.Java
class MinutesToHours { public static void main(String args[]) { int minutes = 150; float hours; hours = (float)minutes/60; System.out.println( "Convert result: " + minutes + " minutes is " + hours + " hours "); } }
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Input/Output
InputOutput.java
Input your name, print out your name Input your age, print out our age Input your height, print out your height Using EasyIn.java
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InputOutput.java (1)
class InputOutput { public static void main(String args[]) { EasyIn easy = new EasyIn(); String name; System.out.print("enter your name: "); name = easy.readString(); System.out.println("Your name is: " + ECE242 Spring 2003 Data Structures in Java, Prof. Gao
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InputOutput.java (2)
(continued)
int age; System.out.print("enter your age: "); age = easy.readInt(); System.out.println("Your age is: " + age );
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InputOutput.java (3)
(continued)
float height; System.out.print("enter your height(feet): "); height = easy.readFloat(); System.out.println("Your height is: " + height + " feet" );
}
}
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