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Chapter 11 The java.io Package |
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PrintStream
Name
PrintStreamSynopsis
- Class Name:
-
java.io.PrintStream
- Superclass:
-
java.io.FilterOutputStream
- Immediate Subclasses:
-
None
- Interfaces Implemented:
-
None
- Availability:
-
JDK 1.0 or later
Description
The PrintStream class provides support for writing string representations of primitive data types and objects to an underlying output stream. As of JDK 1.1, PrintStream uses the system's default encoding scheme to convert characters to bytes and uses the system's own specific line separator, rather than the newline character, for separating lines of text. Although this class is not officially deprecated, its constructors are, and you should use PrintWriter instead of PrintStream in new code.
Prior to JDK 1.1, PrintStream did not handle Unicode characters. Any PrintStream methods that wrote characters only wrote the low eight bits of each character. In addition, prior to JDK 1.1, PrintStream used the newline character to separate lines of text, regardless of the platform. These problems have been corrected as of JDK 1.1.
All of the methods of PrintStream that write multiple times to the underlying output stream handle synchronization internally, so that PrintStream objects are thread-safe.
A PrintStream object is often used to write to a BufferedOutputStream object. Note that you can specify that the PrintStream be flushed every time it writes the line separator or the newline character by using the constructor that takes a boolean argument.
PrintStream objects are often used to report errors. For this reason, the methods of this class do not throw exceptions. Instead, the methods catch any exceptions thrown by any downstream OutputStream objects and set an internal flag, so that the object can remember that a problem occurred. You can query the internal flag by calling the checkError() method.
Class Summary
public class java.io.PrintStream extends java.io.FilterOutputStream {
// Constructors
public PrintStream(OutputStream out); // Deprecated in 1.1
public PrintStream(OutputStream out,
boolean autoFlush); // Deprecated in 1.1
// Public Instance Methods
public boolean checkError();
public void close();
public void flush();
public void print(boolean b);
public void print(char c);
public void print(char[] s);
public void print(double d);
public void print(float f);
public void print(int i);
public void print(long l);
public void print(String s);
public void print(Object obj);
public void println();
public void println(boolean b);
public void println(char c);
public void println(char[] s);
public void println(double d);
public void println(float f);
public void println(int i);
public void println(long l);
public void println(Object obj);
public void println(String s);
public void write(int b);
public void write(byte[] buf, int off, int len);
// Protected Instance Methods
protected void setError(); // New in 1.1
}
Constructors
PrintStream
public PrintStream(OutputStream out)
- Availability
-
Deprecated as of JDK 1.1
- Parameters
-
- out
-
The output stream to use.
- out
- Description
-
This constructor creates a PrintStream object that sends output to the given OutputStream.
public PrintStream(OutputStream out, boolean autoflush)
- Availability
-
Deprecated as of JDK 1.1
- Parameters
-
- out
-
The output stream to use.
- autoflush
-
A boolean value that indicates whether or not the print stream is flushed every time a newline is output.
- out
- Description
-
This constructor creates a PrintStream object that sends output to the given OutputStream. If autoflush is true, every time the PrintStream object writes a newline character or line separator, it calls its flush() method. Note that this is different than with a PrintWriter object, which only calls its flush() method when a println() method is called.
Public Instance Methods
checkError
public boolean checkError()
- Returns
-
true if any error has occurred; false otherwise.
- Description
-
This method flushes any buffered output and returns true if any error has occurred. Once the error flag for a PrintStream object has been set, it is never cleared.
close
public void close()
- Overrides
-
FilterOutputStream.close()
- Description
-
This method closes this print stream and releases any resources associated with the object. The method does this by calling the close() method of the underlying output stream and catching any exceptions that are thrown.
flush
public void flush()
- Overrides
-
FilterOutputStream.flush()
- Description
-
This method flushes this print stream, forcing any bytes that may be buffered to be written to the underlying output stream. The method does this by calling the flush() method of the underlying output stream and catching any exceptions that are thrown.
public void print(boolean b)
- Parameters
-
- b
-
The boolean value to print.
- b
- Description
-
This method writes "true" to the underlying output stream if b is true; otherwise it writes "false".
public void print(char c)
- Parameters
-
- c
-
The char value to print.
- c
- Description
-
This method writes the given character to the underlying output stream.
public void print(char[] s)
- Parameters
-
- s
-
The char array to print.
- s
- Description
-
This method writes the characters in the given array to the underlying output stream.
public void print(double d)
- Parameters
-
- d
-
The double value to print.
- d
- Description
-
This method writes a string representation of the given double value to the underlying output stream. The string representation is identical to the one returned by calling Double.toString(d).
public void print(float f)
- Parameters
-
- f
-
The float value to print.
- f
- Description
-
This method writes a string representation of the given float value to the underlying output stream. The string representation is identical to the one returned by calling Float.toString(f).
public void print(int i)
- Parameters
-
- i
-
The int value to print.
- i
- Description
-
This method writes a string representation of the given int value to the underlying output stream. The string representation is identical to the one returned by calling Integer.toString(i).
public void print(long l)
- Parameters
-
- l
-
The long value to print.
- l
- Description
-
This method writes a string representation of the given long value to the underlying output stream. The string representation is identical to the one returned by calling Long.toString(l).
public void print(Object obj)
- Parameters
-
- obj
-
The Object to print.
- obj
- Description
-
This method writes the string representation of the given Object to the underlying output stream. The string representation is that returned by calling the toString() method of Object.
public void print(String s)
- Parameters
-
- s
-
The String to print.
- s
- Description
-
This method writes the given String to the underlying output stream. If String is null, the method writes "null".
println
public void println()
- Description
-
This method writes a line separator to the underlying output stream.
public void println(boolean b)
- Parameters
-
- b
-
The boolean value to print.
- b
- Description
-
This method writes "true" to the underlying output stream if b is true, otherwise it writes "false". In either case, the string is followed by a line separator.
public void println(char c)
- Parameters
-
- c
-
The char value to print.
- c
- Description
-
This method writes the given character, followed by a line separator, to the underlying output stream.
public void println(char[] s)
- Parameters
-
- s
-
The char array to print.
- s
- Description
-
This method writes the characters in the given array, followed by a line separator, to the underlying output stream.
public void println(double d)
- Parameters
-
- d
-
The double value to print.
- d
- Description
-
This method writes a string representation of the given double value, followed by a line separator, to the underlying output stream. The string representation is identical to the one returned by calling Double.toString(d).
public void println(float f)
- Parameters
-
- f
-
The float value to print.
- f
- Description
-
This method writes a string representation of the given float value, followed by a line separator, to the underlying output stream. The string representation is identical to the one returned by calling Float.toString(f).
public void println(int i)
- Parameters
-
- i
-
The int value to print.
- i
- Description
-
This method writes a string representation of the given int value, followed by a line separator, to the underlying output stream. The string representation is identical to the one returned by calling Integer.toString(i).
public void println(long l)
- Parameters
-
- l
-
The long value to print.
- l
- Description
-
This method writes a string representation of the given long value, followed by a line separator, to the underlying output stream. The string representation is identical to the one returned by calling Long.toString(l).
public void println(Object obj)
- Parameters
-
- obj
-
The Object to print.
- obj
- Description
-
This method writes the string representation of the given Object, followed by a line separator, to the underlying output stream. The string representation is that returned by calling the toString() method of Object.
public void println(String s)
- Parameters
-
- s
-
The String to print.
- s
- Description
-
This method writes the given String, followed by a line separator, to the underlying output stream. If String is null, the method writes "null" followed by a line separator.
write
public void write(int b)
- Parameters
-
- b
-
The value to write to the stream.
- b
- Overrides
-
FilterOutputStream.write(int)
- Description
-
This method writes the lowest eight bits of b to the underlying stream as a byte. The method does this by calling the write() method of the underlying output stream and catching any exceptions that are thrown. If necessary, the method blocks until the byte is written.
public void write(byte b[], int off, int len)
- Parameters
-
- b
-
An array of bytes to write to the stream.
- off
-
An offset into the byte array.
- len
-
The number of bytes to write.
- b
- Overrides
-
FilterOutputStream.write(byte[], int, int)
- Description
-
This method writes the lowest eight bits of each of len bytes from the given array, starting off elements from the beginning of the array, to the underlying output stream. The method does this by calling write(b, off, len) for the underlying output stream and catching any exceptions that are thrown. If necessary, the method blocks until the bytes are written.
Protected Instance Methods
setError
protected void setError()
- Availability
-
New as of JDK 1.1
- Description
-
This method sets the error state of the PrintStream object to true. Any subsequent calls to getError() return true.
Inherited Methods
|
Method |
Inherited From |
Method |
Inherited From |
|---|---|---|---|
|
clone() |
Object |
equals(Object) |
Object |
|
finalize() |
Object |
getClass() |
Object |
|
hashCode() |
Object |
notify() |
Object |
|
notifyAll() |
Object |
toString() |
Object |
|
wait() |
Object |
wait(long) |
Object |
|
wait(long, int) |
Object |
write(byte[]) |
FilterOutputStream |
See Also
Double, FilterOutputStream, Float, Integer, Long, OutputStream
|
 |
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| PipedWriter |  |
PrintWriter |
