1. Chapter 10: I/O Streams Input Streams Output Streams
File streams (File input and File)
Filters (Data input and output)
File class
FileDialog class

2. Input/Output
Cannot expect user to enter all information when starting program (airline program -- enter all flight info??)
Stream - a sequence of characters (either as input or output that we can perform operations to)
write a char
read a char
read a sequence of chars

3. Streams generally connected to files (using FileInputStream or FileOutputStream)
Can also be connected to other objects (Strings, other streams, etc.)
DataInputStream and DataOutputStream are streams that allow more complex manipulations
Include java.io.*;

4. InputStream Abstract class Methods:
int available() throws IOException - returns 0, can be overridden, indicates # available chars
void close() throws IOException - close stream
long skip(long n) throws IOException - skip the next n characters

5. InputStream methods:
int read() throws IOException - gets the next available char from the stream, -1 if none
int read(byte[] bArray) throws IOException, NullPointerException - trys to fill array, returns the number of characters read
int read(byte[] bArray, int offset, int length) throws IOException, NullPointerException, IndexOutOfBoundsException - trys to fill array starting at position offset with up to length chars, returns the number read

6. OutputStream Abstract class Methods:
void close() throws IOException - close stream
long flush() throws IOException - flush buffer
void write(int c) throws IOException - write char c to stream
void write(byte[] bArray) throws IOException, NullPointerException - writes the array of chars
void write(byte[] bArray, int offset, int length) throws IOException, NullPointerException, IndexOutOfBoundsException - writes length chars starting at offset to stream

7. FileInputStream InputStream connected to a file constructors: methods:
FileInputStream(String fname) throws FileNotFoundException, SecurityException - opens InputStream connected to fname
FileInputStream(File f) throws FileNotFoundException, SecurityException - same as above using File class (more later)
methods:
implements methods of InputStream: available, close, skip, 3 reads

8. FileOutputStream OutputStream connected to a file constructors:
FileOutputStream(String fname) throws FileNotFoundException, SecurityException - opens OutputStream connected to fname
FileOutputStream(File f) throws FileNotFoundException, SecurityException - same as above using File class (more later)
methods:
implements methods of OutputStream: close, flush, 3 writes

9. void copyFile(String srcF, String dstF) {
try {
FileInputStream inf = new FileInputStream(srcF);
FileOutputStream outf = newFileOutputStream(dsfF);
int ch;
while ((ch = inf.read()) != -1)
outf.write(ch);
inf.close();
outf.close(); }
catch (Exception e) {
// Announce unable to open files

10. Other InputStream Classes
ByteArrayInputStream - connected to an array of bytes
StringBufferInputStream - connected to a string of characters
PipedInputStream - connected to a pipe command

11. Other Output Stream Classes
ByteArrayOutputStream - connected to an array of bytes
PipedOutputStream - feeding chars to a pipe command

12. Filter Classes Java also provides filter classes
These classes are connected to an input or output stream and allow interpretation of the input/output
Most prevalent are DataInputStream and DataOutputStream

13. DataInputStream Connected to an InputStream (often file) Constructor:
DataInputStream(InputStream in)
Methods:
boolean readBoolean() throws IOException - reads info corresponding to a boolean (1 byte)
similar routines for Byte, Char, Double, Float, Int, Long, Short

14. DataInputStream (cont)
More methods:
int readFully(byte[] bArray) throws IOException, NullPointerException - read in array of chars stopping when full or at EOF
String readLine() throws IOException - read as a string the next sequence of chars until a newline encountered
void skipBytes(int n) throws IOException - skip the next n bytes

15. DataOutputStream Connected to an OutputStream (often file)
Constructor:
DataOutputStream(OutputStream in)
Methods:
void writeBoolean(boolean b) throws IOException - writes b to file
similar routines for Byte, Char, Double, Float, Int, Long, Short

16. DataOutputStream (cont)
More methods:
void writeBytes(byte[] barray) throws IOException - write array of bytes
void writeBytes(String s) throws IOException - write string as array of bytes
void writeChars(String s) throws IOException - similar to writeBytes for string arg

17. class Employee {
private int idnum;
private float salary;
private String name;
void writeToFile(DataOutputStream s) throws IOException {
s.writeInt(idnum);
s.writeFloat(salary);
s.writeString(name + “\n”); }
void readFromFile(DataInputStream s) throws IOException
idnum = s.readInt();
salary = s.readFloat();
name = s.readLine();

18. void writeEmployeeFile(String fname, Employee[] bees, int numEmployees) {
try {
FileOutputStream fos = new FileOutputStream(fname);
DataOutputStream fstream = new DataOutputStream(fos);
int e;
fstream.writeInt(numEmployees);
for (e = 0; e < numEmployees; e++)
bees[e].writeToFile(fstream);
fstream.close(); }
catch IOException {
// report that something went wrong

19. int readEmployeeFile(String fname, Employee[] bees) {
try {
FileInputStream fis = new FileInputStream(fname);
DataInputStream fstream = new DataInputStream(fis);
int e;
int numEmployees;
numEmployees = fstream.readInt();
for (e = 0; e < numEmployees; e++)
bees[e].readFromFile(fstream);
fstream.close();
return numEmployees; }
catch IOException {
// report that something went wrong

20. Other Useful Filters
BufferedInputStream, BufferedOutputStream - reduces I/O with buffering
LineNumberInputStream - adds the feature of knowing the line number as lines read
PushbackInputStream - implements a one char “push back” buffer - good for parsing

21. File Class
Mechanism for exploring files (often used to avoid having exceptions thrown when files not found)
Constructor:
File(String name) - produces a File instance even if the name is not a legal file name

22. Methods: boolean exists() - true if file already exists
boolean isDirectory() - true if directory file
boolean isFile() - true if data file
boolean canRead() - true if file can be read
boolean canWrite() - true if file can be written
long lastModified() - returns a number indicating last modification time (no given structure)

23. Methods: long length() - number of bytes in file
boolean equals(Object obj) - true if arg is file with same name
String[] list() - returns list of files in directory
String[] list(FileNameFilter f) - returns list of acceptable files from directory
boolean delete() - attempts to delete, true if success

24. FileNameFilter Interface
Restrict files in File, FileDialog classes
Implements one method:
boolean accept(File directory, String name) - true if this directory, name acceptable
Example
class JavaSrcFilter implements FileNameFilter {
boolean accept(File d, String s) {
if (s.endswith(“.java”)) return true;
else return false; }

25. FileDialog
Produces a Dialog box that can be used to select files (look depends on system)
In java.awt.FileDialog
constants: LOAD, SAVE (modes)
constructors:
FileDialog(Frame Parent, String mssg) - mssg used to prompt, must have parent frame
FileDialog(Frame Parent, String mssg, int mode) - mode is one of FileDialog.LOAD or SAVE, indicates expected use of file

26. Methods:
String getDirectory() - string corresponding to directory selected
File getFile() - File object corresponding to file selected
void setFileNameFilter(FileNameFilter f) - set filter used to select files
void setDirectory(String s) - set initial directory
void setFile(String s) - set initial file
void getFileNameFilter() - get current filter (null if none)