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List of Java Examples
1. FileOutStream Example: Write to a file
2. FileInputStream Example: Read from a file
3. FileOutputStream Example along with Try With Resources
4. Copy file Utility using Byte Stream Classes (FileInputStream, FileOutputStream)
5. Using Character Stream Class FileWriter to write to a file
6. BufferedInputStream Example
6. DataStream Example (DataInputStream & DataOutputStream)
7. ObjectStream Example
8. Using File Class to view file attributes (Complete path, length, file type(regular/directory)
9. ListDirectory using File Methods (list, listFiles)
10. List all files in a directory and its sub directories
FileOutStream Example: Write to a file
import java.io.FileOutputStream;
public class I01FosExample {
public static void main(String[] args) {
// TODO Auto-generated method stub
try{
FileOutputStream fout=new FileOutputStream("testout.txt");
String s="Welcome to Java Course and Today is Monday(19-Jun-2017)";
byte b[]=s.getBytes();//converting string into byte array
fout.write(b);
fout.close();
System.out.println("success...");
}catch(Exception e){System.out.println(e);}
}
}
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FileInputStream Example: Read from a file
import java.io.FileInputStream;
public class I02FisExample {
public static void main(String[] args) {
// TODO Auto-generated method stub
try{
FileInputStream fin=new FileInputStream("testout.txt");
int i=0;
while((i=fin.read())!=-1){
System.out.print((char)i);
}
fin.close();
}catch(Exception e)
{
System.out.println(e);
}
}
}
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FileOutputStream Example along with Try With Resources
import java.io.FileOutputStream;
public class I03FosExampleTryWithRes {
public static void main(String[] args) {
// TODO Auto-generated method stub
try(FileOutputStream fout=new FileOutputStream("testout12.txt")){
String s="Welcome to Java Course and Try With Resources";
byte b[]=s.getBytes();//converting string into byte array
fout.write(b);
// fout.close();
System.out.println("success...");
}catch(Exception e){System.out.println(e);}
}
}
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Copy file Utility using Byte Stream Classes (FileInputStream, FileOutputStream)
Note:
1) Program Arguments: Source_File_Name Destination_File_Name
2) Converstion of byte array to String
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class I04CopyFile {
public static void main(String[] args) {
// TODO Auto-generated method stub
if ((args.length==0)||(args.length<2)){
System.out.println("Please provide source and destination file");
return;
}
String srcFile=args[0];
String destFile = args[1];
try{
FileInputStream inStream=new FileInputStream(srcFile);
FileOutputStream outStream = new FileOutputStream(destFile);
byte[] buffer = new byte[1024];
int length;
/*copying the contents from input stream to
* output stream using read and write methods
*/
while ((length = inStream.read(buffer)) > 0){
outStream.write(buffer, 0, length);
System.out.println("Buffer length:"+length);
// Convert byte array to String
String str2 = new String(buffer,"UTF-8");
System.out.println(str2);
}
//Closing the input/output file streams
inStream.close();
outStream.close();
System.out.println("File copied successfully!!");
}catch(IOException ioe){
ioe.printStackTrace();
}
}
}
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Using Character Stream Class FileWriter to write to a file
import java.io.FileWriter;
public class I05FileWriterExample {
public static void main(String[] args) {
// TODO Auto-generated method stub
try{
FileWriter fw=new FileWriter("testout12.txt");
String s="Welcome to Java Course and File Writer";
fw.write(s);
fw.close();
System.out.println("File writer success...");
}catch(Exception e){System.out.println(e);}
}
}
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BufferedInputStream Example
import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
public class I06BisExample {
public static void main(String[] args) {
// TODO Auto-generated method stub
BufferedInputStream bis = null;
FileInputStream fis= null;
try
{
//FileInputStream to read the file
fis = new FileInputStream("about.txt");
/*Passed the FileInputStream to BufferedInputStream
*For Fast read using the buffer array.*/
bis = new BufferedInputStream(fis);
/*available() method of BufferedInputStream
* returns 0 when there are no more bytes
* present in the file to be read*/
while( bis.available() > 0 ){
System.out.print((char)bis.read());
}
}catch(FileNotFoundException fnfe)
{
System.out.println("The specified file not found" + fnfe);
}
catch(IOException ioe)
{
System.out.println("I/O Exception: " + ioe);
}
finally
{
try{
if(bis != null && fis!=null)
{
fis.close();
bis.close();
}
}catch(IOException ioe)
{
System.out.println("Error in InputStream close(): " + ioe);
}
}
}
}
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DataStream Example (DataInputStream & DataOutputStream)
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class I06DataInputStream {
public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
DataOutputStream dataOutputStream =
new DataOutputStream(
new FileOutputStream("dataStream.bin"));
dataOutputStream.writeInt(123);
dataOutputStream.writeFloat(123.45F);
dataOutputStream.writeLong(789);
dataOutputStream.close();
DataInputStream dataInputStream =
new DataInputStream(
new FileInputStream("dataStream.bin"));
int int123 = dataInputStream.readInt();
float float12345 = dataInputStream.readFloat();
long long789 = dataInputStream.readLong();
dataInputStream.close();
System.out.println("int123 = " + int123);
System.out.println("float12345 = " + float12345);
System.out.println("long789 = " + long789);
}
}
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ObjectStream Example
Note: Use of serialazable. Please delete implements serializable and try running program.
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
public class I08ObjectStreamExample {
public static class Person implements Serializable {
public String name = null;
public int age = 0;
}
public static void main(String[] args) throws FileNotFoundException, IOException, ClassNotFoundException {
// TODO Auto-generated method stub
ObjectOutputStream objectOutputStream =
new ObjectOutputStream(new FileOutputStream("person.dat"));
Person person = new Person();
person.name = "Chandan Kumar";
person.age = 19;
objectOutputStream.writeObject(person);
objectOutputStream.close();
ObjectInputStream objectInputStream =
new ObjectInputStream(new FileInputStream("person.dat"));
Person personRead = (Person) objectInputStream.readObject();
objectInputStream.close();
System.out.println(personRead.name);
System.out.println(personRead.age);
}
}
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Using File Class to view file attributes (Complete path, length,
file type(regular/directory)
import java.io.File;
public class I11FileAttributes {
public static void main(String[] args) {
// TODO Auto-generated method stub
File f1 = new File("testout.txt");
if (f1.isFile()){
System.out.println("This is a regular file");
}
System.out.println(f1.getAbsolutePath());
System.out.println(f1.length());
System.out.println(f1.getName());
System.out.println(f1.isDirectory());
}
}
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ListDirectory using File Methods (list, listFiles)
Note: list returns File Names String array whereas listFiles return File object array
import java.io.File;
public class I12ListDirectory {
public static void main(String[] args) {
// TODO Auto-generated method stub
File f2 = new File("C:");
System.out.println(f2.getAbsolutePath());
if (f2.isDirectory())
{
String[] list=f2.list();
for (String x:list)
System.out.println(x);
File[] f3= f2.listFiles();
for(File x: f3)
{
System.out.println(x.getName()+":"+x.length() );
}
}
}
}
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List all files in a directory and its sub directories
Note: Please note the usage of recursion here..
import java.io.File;
import java.io.IOException;
public class I14ListAllFiles {
public static void main(String[] args) {
// TODO Auto-generated method stub
File currentDir = new File("D:\\Java-Pgms"); // current directory
showDirectoryContents(currentDir);
}
public static void showDirectoryContents(File dir) {
try {
File[] files = dir.listFiles();
for (File file : files) {
if (file.isDirectory()) {
System.out.println("directory:" + file.getCanonicalPath());
showDirectoryContents(file);
} else {
System.out.println(" file:" + file.getCanonicalPath());
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
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