Java IO.pdf - Nguyen Dang Binh

Java I/O
The read() and available() methods work exactly as with normal input streams. However,
they first attempt to read from the pushback buffer.
public int read() throws IOException
public int read(byte[] data, int offset, int length) throws IOException
public int available() throws IOException
6.5 Print Streams
System.out and System.err are instances of the java.io.PrintStream class. This is a
subclass of FilterOutputStream that converts numbers and objects to text. System.out is
primarily used for simple, character-mode applications and for debugging. Its raison d'être is
convenience, not robustness; print streams ignore many issues involved in internationalization
and error checking. This makes System.out easy to use in quick and dirty hacks and simple
examples, while simultaneously making it unsuitable for production code, which should use
the java.io.PrintWriter class (discussed in Chapter 15) instead.
The PrintStream class has print() and println() methods that handle every Java data
type. The print() and println() methods differ only in that println() prints a platformspecific
line terminator after printing its arguments and print() does not. These methods are:
public void print(boolean b)
public void print(char c)
public void print(int i)
public void print(long l)
public void print(float f)
public void print(double d)
public void print(char[] s)
public void print(String s)
public void print(Object o)
public void println()
public void println(boolean b)
public void println(char c)
public void println(int i)
public void println(long l)
public void println(float f)
public void println(double d)
public void println(char[] s)
public void println(String s)
public void println(Object o)
Anything at all can be passed to a print() method; whatever argument you give is
guaranteed to match at least one of these methods. Object types are converted to strings by
invoking their toString() method. Primitive types are converted with the appropriate
String.valueOf() method.
One aspect of making System.out simple for quick jobs is not in the PrintStream class at
all but in the compiler. Because Java overloads the + operator to signify concatenation of
strings, primitive data types, and objects, you can pass multiple variables to the print() and
println() methods, which are then converted to strings and concatenated . For example,
consider the line:
System.out.println("As of " + (new Date()) + " there have been over "
+ hits + " hits on the web site." );
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