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Revised: Mon Mar 28 12:30:19 CDT 2016
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Earlier modules have touched briefly on the topic of variables. This module discusses Java variables in depth.
I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view the Figuresand Listings while you are reading about them.
The first step
The first step in learning to use a new programming language is usually to learn the foundation concepts such as
This and several future modules concentrate on that foundation.
A sample program
The module begins with a sample Java program named simple1 . The user is asked to enter some text and to terminate with the # character.
(This program contains a lot of code that you are not yet prepared to understand. For the time being, just concentrate on the use of variables in theprogram. You will learn about the other aspects of the program in future modules.)
The program loops, saving individual characters until encountering the # character. When itencounters the # character, it terminates and displays the character entered immediately prior to the # character.
A complete listing of the program named simple1 is provided in Listing 1 . Discussions of selected portions of theprogram are presented later in the module.
| Listing 1 . Source code for the program named simple1. |
|---|
/*File simple1.java Copyright 1997, R.G.Baldwin
This Java application reads bytes from the keyboard untilencountering the integer representation of '#'. At
the end of each iteration, it saves the byte received andgoes back to get the next byte.
When the '#' is entered, the program terminates input anddisplays the character which was entered before the #.
**********************************************************/class simple1 { //define the controlling class
//It is necessary to declare that this method// can throw the exception shown below (or catch it).
public static void main(String[]args) //define main
throws java.io.IOException {//It is necessary to initialize ch2 to avoid a compiler
// error (possibly uninitialized variable) at the// statement which displays ch2.
int ch1, ch2 = '0';System.out.println(
"Enter some text, terminate with #");//Get and save individual bytes
while( (ch1 = System.in.read() ) != '#')ch2 = ch1;
//Display the character immediately before the #System.out.println(
"The char before the # was " + (char)ch2);}//end main
}//End simple1 class. |
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