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
platform-specific 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 ...
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