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We have provided EasyReader and EasyWriter
classes to supplement Java's stream I/O classes. EasyReader
lets you read numbers, characters, words, and strings from the console and
from a text file. EasyWriter lets you write these data
elements into a text file (or append data to an existing file). These
classes are online and on your student disk, in the EasyReader
folder.
You can combine these two classes into a com.skylit.io
package and install it properly, but it may be easier at first to simply
copy the one(s) you need into your project folder. Each of these classes
has a simple example in its source file. You can also reinstate the
commented out package directive at the top of each file and
generate standard HTML documentation from EasyReader.java and
EasyWriter.java using javadoc.
To open the standard input stream for reading keyboard input use <![CDATA[ EasyReader console = new EasyReader();
]]>console is the name you give to the input stream (can
be anything you like).
To open a text file for reading use <![CDATA[ EasyReader inFile = new EasyReader(fileName);
]]>inFile is the name you give to the input stream
associated with the file (can be anything you like); fileName
is a String.
Call the bad() method to check the status of the file. It
returns true if the file is not opened properly or if there
is an error or end of file; false otherwise. For example: <![CDATA[ EasyReader inFile = new EasyReader(fileName);
if (inFile.bad())
{
System.err.println("Can't open " + fileName);
System.exit(1);
}
]]>
Examples for reading data from the keyboard or a file: <![CDATA[ int n = console.readInt(); // reads an integer
double x = console.readDouble(); // reads a double
char ch = inFile.readChar(); // reads any character,
// including whitespace
String word = inFile.readWord(); // reads a contiguous string of
// non-whitespace characters
// Read and process all lines from a file:
String line;
while ((line = inFile.readLine()) != null)
{
// process line:
...
}
]]>Note:
readInt, readDouble,
readChar, and readWord methods do not consume
the end of the line after reading the last item. Call
readLine to get rid of the tail of the line (even if only
the newline character is left) before calling
readLine on the next line.
Call inFile.close() to close the file.
To open a text file for writing use <![CDATA[ EasyWriter outFile = new EasyWriter(fileName);
]]>(or <![CDATA[ EasyWriter outFile = new EasyWriter(fileName, "app");
]]>if you want to append data to an existing file).
outFile is the name you give to the output stream associated
with the file (can be anything you like); fileName is a
String.
Be careful:
new EasyWriter(fileName) wipes out the contents
of the file if it already exists.
Call the bad() method that returns true if
the file is not created (or opened for appending) properly;
false otherwise.
Use print and println methods, the same as in
System.out, to write data to a file. For example: <![CDATA[ outFile.print("x = ");
outFile.println(x);
]]>or <![CDATA[ outFile.println("x = " + x);
]]>Call outFile.println() to write a blank line.
Call outFile.close() to close the file.
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