Java IO operations: Fileinputstream,fileoutputstream,filereader,filewriter instances

FileInputStream

 

2. <span style="Font-family:verdana;"  >import java.io.File;
4. Import Java.io.FileInputStream;
6. Import Java.io.InputStream;
10. Public class Testfileinputstream {
12. public static void Main (string[] args) throws Exception { //exception thrown, not processed
14. //1th step: Use the file class to find a document
16. File F = new file ("C:" + File.separator + "test.txt"); Declaring a File object
18. //2nd step: Instantiating a parent class object from a subclass
20. InputStream input = null;
22. //Prepare an input object for instantiation by object polymorphism
24. input = new FileInputStream (f);
26. //3rd step: Read, all the contents are read in this array
28. byte b[] = new byte[1024];
30. int len = Input.read (b);
32. //4th step: Turn off the input stream
34. Input.close ();
36. //change byte array to string output
38. System.out.println ("Length of the read-in data:" + len);
40. System.out.println ("content:" + new String (b, 0, Len));
42. }
44. }</span>

FileOutputStream

 

2. <span style="Font-family:verdana;"  >import java.io.File;
4. Import Java.io.FileOutputStream;
6. Import Java.io.OutputStream;
10. Public class Testfileoutputstream {
12. public static void Main (string[] args) throws Exception { //exception thrown, not processed
14. //1th step: Use the file class to find a document
16. File F = new file ("C:" + File.separator + "test.txt"); //Declare file object
18. //2nd step: Instantiating a parent class object from a subclass
20. OutputStream out = null;
22. //Prepare an Output object, and instantiate it through the polymorphism of the object
24. out = new FileOutputStream (f);
26. //3rd step: Write, prepare a string
28. String str = "Hello world!!!";
30. //can only output a byte array, so the string becomes a byte array
32. byte b[] = Str.getbytes ();
34. //Output The content, save the file
36. Out.write (b);
38. //4th step: Turn off the output stream
40. Out.close ();
42. }
44. }</span>

FileReader

 

2. <span style="Font-family:verdana;"  >import java.io.File;
4. Import Java.io.FileReader;
6. Import Java.io.Reader;
10. Public class Testfilereader {
12. public static void Main (string[] args) throws Exception { //exception thrown, not processed
14. ///1th step: Use the file class to locate a document that declares a Files object
16. File F = new file ("D:" + File.separator + "test.txt");
18. //2nd step: Instantiating a parent class object from a subclass
20. Reader reader = null;
22. //Prepare an input object for instantiation by object polymorphism
24. reader = new FileReader (f);
26. //3rd step: Read, all the contents are read in this array
28. char c[] = new char[1024];
30. int len = Reader.read (c);
32. //4th step: Turn off the input stream
34. Reader.close ();
36. //Change char array to string output
38. System.out.println ("content:" + new String (c, 0, Len));
40. }
42. }</span>

FileWriter

 

2. <span style="Font-family:verdana;"  >import java.io.File;
4. Import Java.io.FileWriter;
6. Import Java.io.Writer;
10. Public class Testfilewriter {
12. public static void Main (string[] args) throws Exception { //exception thrown, not processed
14. ///1th step: Use the file class to locate a document that declares a Files object
16. File F = new file ("C:" + File.separator + "test.txt");
18. //2nd step: Instantiating a parent class object from a subclass
20. Writer out = null;
22. //Prepare an Output object, and instantiate it through the polymorphism of the object
24. out = new FileWriter (f);
26. //3rd step: Write, prepare a string
28. String str = "Hello world!!!";
30. Out.write (str);
32. Out.flush ();
34. //4th step: Turn off the output stream
36. Out.close ();
38. }
40. }</span>

Java IO operations: Fileinputstream,fileoutputstream,filereader,filewriter instances