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IO example
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‎RandomProblems/src/sporadic/IO_example/JavaFileExample.java

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package sporadic.IO_example;
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import java.io.File;
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/**
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* This is a class to demo File class in java.
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*
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* A directory is a File
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*
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* which can contain a list of other files and directories. You use File object
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* to create directories, to list down files available in a directory. For
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* complete detail check a list of all the methods which you can call on File
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* object and what are related to directories.
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*
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* Java automatically takes care of path separators on UNIX and Windows as per
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* conventions. If you use a forward slash (/) on a Windows version of Java, the
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* path will still resolve correctly.
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*
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* @author jiahuan
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*
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*/
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public class JavaFileExample {
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private static final String DIRECTORY_TO_CREATE = "/tmp/fileCreatedFromRunning-JavaFileExample";
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private static final String DIRECTORY_TO_LIST = "/Users/SteveSun/Downloads";
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public static void main(String[] args) {
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mkDirectory(DIRECTORY_TO_CREATE);
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listDirectories(DIRECTORY_TO_LIST);
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}
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/**
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* @param dir TODO
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*
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*/
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static void mkDirectory(String DIRECTORY_TO_CREATE) {
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File d = new File(DIRECTORY_TO_CREATE);
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// Create directory now.
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d.mkdirs();
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}
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/**
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* You can use list() method provided by File object to list down all the
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* files and directories available in a directory as follows:
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* @param dir TODO
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*/
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static void listDirectories(String DIRECTORY_TO_LIST) {
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File file = null;
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String[] paths;
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try {
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// create new file object
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file = new File(DIRECTORY_TO_LIST);
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// array of files and directory
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paths = file.list();
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// for each name in the path array
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for (String path : paths) {
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// prints filename and directory name
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System.out.println(path);
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}
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} catch (Exception e) {
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e.printStackTrace();
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}
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}
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}

‎RandomProblems/src/sporadic/IO_example/JavaIOExample.java

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package sporadic.IO_example;
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import java.io.FileInputStream;
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import java.io.FileNotFoundException;
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import java.io.FileOutputStream;
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import java.io.FileReader;
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import java.io.FileWriter;
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import java.io.IOException;
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import java.io.InputStreamReader;
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public class JavaIOExample {
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private static final String INPUT = "/Users/SteveSun/Downloads/bash.sh";
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// "/tmp/input.txt";
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private static final String OUTPUT = "/tmp/output.txt";
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public static void main(String[] args) throws IOException {
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byteStreamsIO();
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// characterStreamsIO();
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// standardStreamsIO();
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}
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/**
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* Java byte streams are used to perform input and output of 8-bit bytes.
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* Though there are many classes related to byte streams but the most
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* frequently used classes are: FileInputStream and FileOutputStream.
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* Following is an example which makes use of these two classes to copy an
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* input file into an output file:
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*
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* @throws IOException
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*/
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static void byteStreamsIO() throws IOException {// This type is
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// package-level access,
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// without public, protected
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// and private keywords,
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// this is package-level
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// method
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FileInputStream fis = null;
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FileOutputStream fos = null;
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try {
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fis = new FileInputStream(INPUT);
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fos = new FileOutputStream(OUTPUT);
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int c;
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while ((c = fis.read()) != -1) {
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fos.write(c);
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}
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} catch (FileNotFoundException e) {
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e.printStackTrace();
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} finally {
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if (fis != null) {
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fis.close();
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}
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if (fos != null) {
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fos.close();
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}
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}
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}
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/**
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* Java Byte streams are used to perform input and output of 8-bit bytes,
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* where as Java Character streams are used to perform input and output for
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* 16-bit unicode. Though there are many classes related to character
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* streams but the most frequently used classes are: FileReader and
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* FileWriter Though internally FileReader uses FileInputStream and
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* FileWriter uses FileOutputStream but here major difference is that
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* FileReader reads two bytes at a time and FileWriter writes two bytes at a
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* time.
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*
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* @throws FileNotFoundException
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* @throws IOException
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*/
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static void characterStreamsIO() throws FileNotFoundException, IOException {
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FileReader in = null;
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FileWriter out = null;
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try {
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in = new FileReader(INPUT);
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out = new FileWriter(OUTPUT);
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int c;
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while ((c = in.read()) != -1) {
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out.write(c);
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}
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} finally {
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if (in != null) {
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in.close();
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}
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if (out != null) {
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out.close();
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}
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}
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}
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/**
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* All the programming languages provide support for standard I/O where
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* user's program can take input from a keyboard and then produce output on
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* the computer screen. If you are aware if C or C++ programming languages,
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* then you must be aware of three standard devices STDIN, STDOUT and
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* STDERR. Similar way Java provides following three standard streams
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*
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* Standard Input: This is used to feed the data to user's program and
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* usually a keyboard is used as standard input stream and represented as
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* System.in.
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*
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* Standard Output: This is used to output the data produced by the user's
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* program and usually a computer screen is used to standard output stream
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* and represented as System.out.
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*
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* Standard Error: This is used to output the error data produced by the
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* user's program and usually a computer screen is used to standard error
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* stream and represented as System.err.
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*
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* Following is a simple program which creates InputStreamReader to read
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* standard input stream until the user types a "q":
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*
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* @throws IOException
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*/
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static void standardStreamsIO() throws IOException {
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InputStreamReader isr = null;
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try {
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isr = new InputStreamReader(System.in);
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System.out.println("Enter characters, 'q' to quit.");
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char c;
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do {
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c = (char) isr.read();
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System.out.print(c);
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} while (c != 'q');
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} finally {
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if (isr != null) {
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isr.close();
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}
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System.out.println("\nProgram stopped.");
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}
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}
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}

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