程序包 java.io

类 PrintWriter

java.lang.Object

java.io.Writer

java.io.PrintWriter

所有已实现的接口:

Closeable, Flushable, Appendable, AutoCloseable

public class PrintWriter
extends Writer

Prints formatted representations of objects to a text-output stream. This class implements all of the print methods found in PrintStream. It does not contain methods for writing raw bytes, for which a program should use unencoded byte streams.

Unlike the PrintStream class, if automatic flushing is enabled it will be done only when one of the println, printf, or format methods is invoked, rather than whenever a newline character happens to be output. These methods use the platform's own notion of line separator rather than the newline character.

Methods in this class never throw I/O exceptions, although some of its constructors may. The client may inquire as to whether any errors have occurred by invoking checkError().

从以下版本开始:

JDK1.1

字段概要

字段

限定符和类型	字段	说明
protected Writer	out	The underlying character-output stream of this PrintWriter.

从类继承的字段 java.io.Writer

lock

构造器概要

构造器

构造器	说明
PrintWriter(File file)	Creates a new PrintWriter, without automatic line flushing, with the specified file.
PrintWriter(File file, String csn)	Creates a new PrintWriter, without automatic line flushing, with the specified file and charset.
PrintWriter(OutputStream out)	Creates a new PrintWriter, without automatic line flushing, from an existing OutputStream.
PrintWriter(OutputStream out, boolean autoFlush)	Creates a new PrintWriter from an existing OutputStream.
PrintWriter(Writer out)	Creates a new PrintWriter, without automatic line flushing.
PrintWriter(Writer out, boolean autoFlush)	Creates a new PrintWriter.
PrintWriter(String fileName)	Creates a new PrintWriter, without automatic line flushing, with the specified file name.
PrintWriter(String fileName, String csn)	Creates a new PrintWriter, without automatic line flushing, with the specified file name and charset.

方法概要

限定符和类型	方法	说明
PrintWriter	append(char c)	Appends the specified character to this writer.
PrintWriter	append(CharSequence csq)	Appends the specified character sequence to this writer.
PrintWriter	append(CharSequence csq, int start, int end)	Appends a subsequence of the specified character sequence to this writer.
boolean	checkError()	Flushes the stream if it's not closed and checks its error state.
protected void	clearError()	Clears the error state of this stream.
void	close()	Closes the stream and releases any system resources associated with it.
void	flush()	Flushes the stream.
PrintWriter	format(String format, Object... args)	Writes a formatted string to this writer using the specified format string and arguments.
PrintWriter	format(Locale l, String format, Object... args)	Writes a formatted string to this writer using the specified format string and arguments.
void	print(boolean b)	Prints a boolean value.
void	print(char c)	Prints a character.
void	print(char[] s)	Prints an array of characters.
void	print(double d)	Prints a double-precision floating-point number.
void	print(float f)	Prints a floating-point number.
void	print(int i)	Prints an integer.
void	print(long l)	Prints a long integer.
void	print(Object obj)	Prints an object.
void	print(String s)	Prints a string.
PrintWriter	printf(String format, Object... args)	A convenience method to write a formatted string to this writer using the specified format string and arguments.
PrintWriter	printf(Locale l, String format, Object... args)	A convenience method to write a formatted string to this writer using the specified format string and arguments.
void	println()	Terminates the current line by writing the line separator string.
void	println(boolean x)	Prints a boolean value and then terminates the line.
void	println(char x)	Prints a character and then terminates the line.
void	println(char[] x)	Prints an array of characters and then terminates the line.
void	println(double x)	Prints a double-precision floating-point number and then terminates the line.
void	println(float x)	Prints a floating-point number and then terminates the line.
void	println(int x)	Prints an integer and then terminates the line.
void	println(long x)	Prints a long integer and then terminates the line.
void	println(Object x)	Prints an Object and then terminates the line.
void	println(String x)	Prints a String and then terminates the line.
protected void	setError()	Indicates that an error has occurred.
void	write(char[] buf)	Writes an array of characters.
void	write(char[] buf, int off, int len)	Writes A Portion of an array of characters.
void	write(int c)	Writes a single character.
void	write(String s)	Writes a string.
void	write(String s, int off, int len)	Writes a portion of a string.

从类继承的方法 java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

字段详细资料

out

protected Writer out

The underlying character-output stream of this PrintWriter.

从以下版本开始:

1.2

构造器详细资料

PrintWriter

public PrintWriter(Writer out)

Creates a new PrintWriter, without automatic line flushing.

参数:

out - A character-output stream

PrintWriter

public PrintWriter(Writer out,
                   boolean autoFlush)

Creates a new PrintWriter.

参数:

out - A character-output stream

autoFlush - A boolean; if true, the println, printf, or format methods will flush the output buffer

PrintWriter

public PrintWriter(OutputStream out)

Creates a new PrintWriter, without automatic line flushing, from an existing OutputStream. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will convert characters into bytes using the default character encoding.

参数:

out - An output stream

另请参阅:

OutputStreamWriter(java.io.OutputStream)

PrintWriter

public PrintWriter(OutputStream out,
                   boolean autoFlush)

Creates a new PrintWriter from an existing OutputStream. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will convert characters into bytes using the default character encoding.

参数:

out - An output stream

autoFlush - A boolean; if true, the println, printf, or format methods will flush the output buffer

另请参阅:

OutputStreamWriter(java.io.OutputStream)

PrintWriter

public PrintWriter(String fileName)
            throws FileNotFoundException

Creates a new PrintWriter, without automatic line flushing, with the specified file name. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will encode characters using the default charset for this instance of the Java virtual machine.

参数:

fileName - The name of the file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.

抛出:

FileNotFoundException - If the given string does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file

SecurityException - If a security manager is present and SecurityManager#checkWrite denies write access to the file

从以下版本开始:

1.5

PrintWriter

public PrintWriter(String fileName,
                   String csn)
            throws FileNotFoundException,
                   UnsupportedEncodingException

Creates a new PrintWriter, without automatic line flushing, with the specified file name and charset. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will encode characters using the provided charset.

参数:

fileName - The name of the file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.

csn - The name of a supported charset

抛出:

FileNotFoundException - If the given string does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file

SecurityException - If a security manager is present and SecurityManager#checkWrite denies write access to the file

UnsupportedEncodingException - If the named charset is not supported

从以下版本开始:

1.5

PrintWriter

public PrintWriter(File file)
            throws FileNotFoundException

Creates a new PrintWriter, without automatic line flushing, with the specified file. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will encode characters using the default charset for this instance of the Java virtual machine.

参数:

file - The file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.

抛出:

FileNotFoundException - If the given file object does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file

SecurityException - If a security manager is present and SecurityManager#checkWrite denies write access to the file

从以下版本开始:

1.5

PrintWriter

public PrintWriter(File file,
                   String csn)
            throws FileNotFoundException,
                   UnsupportedEncodingException

Creates a new PrintWriter, without automatic line flushing, with the specified file and charset. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will encode characters using the provided charset.

参数:

file - The file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.

csn - The name of a supported charset

抛出:

FileNotFoundException - If the given file object does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file

SecurityException - If a security manager is present and SecurityManager#checkWrite denies write access to the file

UnsupportedEncodingException - If the named charset is not supported

从以下版本开始:

1.5

方法详细资料

flush

public void flush()

Flushes the stream.

指定者:

flush 在接口中 Flushable

指定者:

flush 在类中 Writer

另请参阅:

checkError()

close

public void close()

Closes the stream and releases any system resources associated with it. Closing a previously closed stream has no effect.

指定者:

close 在接口中 AutoCloseable

指定者:

close 在接口中 Closeable

指定者:

close 在类中 Writer

另请参阅:

checkError()

checkError

public boolean checkError()

Flushes the stream if it's not closed and checks its error state.

返回:

true if the print stream has encountered an error, either on the underlying output stream or during a format conversion.

setError

protected void setError()

Indicates that an error has occurred.

This method will cause subsequent invocations of checkError() to return true until clearError() is invoked.

clearError

protected void clearError()

Clears the error state of this stream.

This method will cause subsequent invocations of checkError() to return false until another write operation fails and invokes setError().

从以下版本开始:

1.6

write

public void write(int c)

Writes a single character.

覆盖:

write 在类中 Writer

参数:

c - int specifying a character to be written.

write

public void write(char[] buf,
                  int off,
                  int len)

Writes A Portion of an array of characters.

指定者:

write 在类中 Writer

参数:

buf - Array of characters

off - Offset from which to start writing characters

len - Number of characters to write

write

public void write(char[] buf)

Writes an array of characters. This method cannot be inherited from the Writer class because it must suppress I/O exceptions.

覆盖:

write 在类中 Writer

参数:

buf - Array of characters to be written

write

public void write(String s,
                  int off,
                  int len)

Writes a portion of a string.

覆盖:

write 在类中 Writer

参数:

s - A String

off - Offset from which to start writing characters

len - Number of characters to write

write

public void write(String s)

Writes a string. This method cannot be inherited from the Writer class because it must suppress I/O exceptions.

覆盖:

write 在类中 Writer

参数:

s - String to be written

print

public void print(boolean b)

Prints a boolean value. The string produced by String.valueOf(boolean) is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.

参数:

b - The boolean to be printed

print

public void print(char c)

Prints a character. The character is translated into one or more bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.

参数:

c - The char to be printed

print

public void print(int i)

Prints an integer. The string produced by String.valueOf(int) is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.

参数:

i - The int to be printed

另请参阅:

Integer.toString(int)

print

public void print(long l)

Prints a long integer. The string produced by String.valueOf(long) is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.

参数:

l - The long to be printed

另请参阅:

Long.toString(long)

print

public void print(float f)

Prints a floating-point number. The string produced by String.valueOf(float) is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.

参数:

f - The float to be printed

另请参阅:

Float.toString(float)

print

public void print(double d)

Prints a double-precision floating-point number. The string produced by String.valueOf(double) is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.

参数:

d - The double to be printed

另请参阅:

Double.toString(double)

print

public void print(char[] s)

Prints an array of characters. The characters are converted into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.

参数:

s - The array of chars to be printed

抛出:

NullPointerException - If s is null

print

public void print(String s)

Prints a string. If the argument is null then the string "null" is printed. Otherwise, the string's characters are converted into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.

参数:

s - The String to be printed

print

public void print(Object obj)

Prints an object. The string produced by the String.valueOf(Object) method is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.

参数:

obj - The Object to be printed

另请参阅:

Object.toString()

println

public void println()

Terminates the current line by writing the line separator string. The line separator string is defined by the system property line.separator, and is not necessarily a single newline character ('\n').

println

public void println(boolean x)

Prints a boolean value and then terminates the line. This method behaves as though it invokes print(boolean) and then println().

参数:

x - the boolean value to be printed

println

public void println(char x)

Prints a character and then terminates the line. This method behaves as though it invokes print(char) and then println().

参数:

x - the char value to be printed

println

public void println(int x)

Prints an integer and then terminates the line. This method behaves as though it invokes print(int) and then println().

参数:

x - the int value to be printed

println

public void println(long x)

Prints a long integer and then terminates the line. This method behaves as though it invokes print(long) and then println().

参数:

x - the long value to be printed

println

public void println(float x)

Prints a floating-point number and then terminates the line. This method behaves as though it invokes print(float) and then println().

参数:

x - the float value to be printed

println

public void println(double x)

Prints a double-precision floating-point number and then terminates the line. This method behaves as though it invokes print(double) and then println().

参数:

x - the double value to be printed

println

public void println(char[] x)

Prints an array of characters and then terminates the line. This method behaves as though it invokes print(char[]) and then println().

参数:

x - the array of char values to be printed

println

public void println(String x)

Prints a String and then terminates the line. This method behaves as though it invokes print(java.lang.String) and then println().

参数:

x - the String value to be printed

println

public void println(Object x)

Prints an Object and then terminates the line. This method calls at first String.valueOf(x) to get the printed object's string value, then behaves as though it invokes print(java.lang.String) and then println().

参数:

x - The Object to be printed.

printf

public PrintWriter printf(String format,
                          Object... args)

A convenience method to write a formatted string to this writer using the specified format string and arguments. If automatic flushing is enabled, calls to this method will flush the output buffer.

An invocation of this method of the form out.printf(format, args) behaves in exactly the same way as the invocation

     out.format(format, args) 

参数:

format - A format string as described in Format string syntax.

args - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by The Java™ Virtual Machine Specification. The behaviour on a null argument depends on the conversion.

返回:

This writer

抛出:

IllegalFormatException - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the formatter class specification.

NullPointerException - If the format is null

从以下版本开始:

1.5

printf

public PrintWriter printf(Locale l,
                          String format,
                          Object... args)

A convenience method to write a formatted string to this writer using the specified format string and arguments. If automatic flushing is enabled, calls to this method will flush the output buffer.

An invocation of this method of the form out.printf(l, format, args) behaves in exactly the same way as the invocation

     out.format(l, format, args) 

参数:

l - The locale to apply during formatting. If l is null then no localization is applied.

format - A format string as described in Format string syntax.

args - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by The Java™ Virtual Machine Specification. The behaviour on a null argument depends on the conversion.

返回:

This writer

抛出:

IllegalFormatException - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the formatter class specification.

NullPointerException - If the format is null

从以下版本开始:

1.5

format

public PrintWriter format(String format,
                          Object... args)

Writes a formatted string to this writer using the specified format string and arguments. If automatic flushing is enabled, calls to this method will flush the output buffer.

The locale always used is the one returned by Locale.getDefault(), regardless of any previous invocations of other formatting methods on this object.

参数:

format - A format string as described in Format string syntax.

args - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by The Java™ Virtual Machine Specification. The behaviour on a null argument depends on the conversion.

返回:

This writer

抛出:

IllegalFormatException - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the Formatter class specification.

NullPointerException - If the format is null

从以下版本开始:

1.5

format

public PrintWriter format(Locale l,
                          String format,
                          Object... args)

Writes a formatted string to this writer using the specified format string and arguments. If automatic flushing is enabled, calls to this method will flush the output buffer.

参数:

l - The locale to apply during formatting. If l is null then no localization is applied.

format - A format string as described in Format string syntax.

args - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by The Java™ Virtual Machine Specification. The behaviour on a null argument depends on the conversion.

返回:

This writer

抛出:

IllegalFormatException - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the formatter class specification.

NullPointerException - If the format is null

从以下版本开始:

1.5

append

public PrintWriter append(CharSequence csq)

Appends the specified character sequence to this writer.

An invocation of this method of the form out.append(csq) behaves in exactly the same way as the invocation

     out.write(csq.toString()) 

Depending on the specification of toString for the character sequence csq, the entire sequence may not be appended. For instance, invoking the toString method of a character buffer will return a subsequence whose content depends upon the buffer's position and limit.

指定者:

append 在接口中 Appendable

覆盖:

append 在类中 Writer

参数:

csq - The character sequence to append. If csq is null, then the four characters "null" are appended to this writer.

返回:

This writer

从以下版本开始:

1.5

append

public PrintWriter append(CharSequence csq,
                          int start,
                          int end)

Appends a subsequence of the specified character sequence to this writer.

An invocation of this method of the form out.append(csq, start, end) when csq is not null, behaves in exactly the same way as the invocation

     out.write(csq.subSequence(start, end).toString()) 

指定者:

append 在接口中 Appendable

覆盖:

append 在类中 Writer

参数:

csq - The character sequence from which a subsequence will be appended. If csq is null, then characters will be appended as if csq contained the four characters "null".

start - The index of the first character in the subsequence

end - The index of the character following the last character in the subsequence

返回:

This writer

抛出:

IndexOutOfBoundsException - If start or end are negative, start is greater than end, or end is greater than csq.length()

从以下版本开始:

1.5

append

public PrintWriter append(char c)

Appends the specified character to this writer.

An invocation of this method of the form out.append(c) behaves in exactly the same way as the invocation

     out.write(c) 

指定者:

append 在接口中 Appendable

覆盖:

append 在类中 Writer

参数:

c - The 16-bit character to append

返回:

This writer

从以下版本开始:

1.5