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Class ByteArrayOutputStream

java.lang.Object

java.io.OutputStream

java.io.ByteArrayOutputStream

All Implemented Interfaces:: Closeable, Flushable, AutoCloseable

public class ByteArrayOutputStream extends OutputStream

This class implements an output stream in which the data is written into a byte array. The buffer automatically grows as data is written to it. The data can be retrieved using toByteArray() and toString().

Closing a ByteArrayOutputStream has no effect. The methods in this class can be called after the stream has been closed without generating an IOException.

Since:: 1.0

Field Summary

Modifier and Type	Field	Description
`protected byte[]`	`buf`	The buffer where data is stored.
`protected int`	`count`	The number of valid bytes in the buffer.

Constructor Summary

Constructor	Description
`ByteArrayOutputStream()`	Creates a new `ByteArrayOutputStream`.
`ByteArrayOutputStream(int size)`	Creates a new `ByteArrayOutputStream`, with a buffer capacity of the specified size, in bytes.

Method Summary

Modifier and Type	Method	Description
`void`	`close()`	Closing a `ByteArrayOutputStream` has no effect.
`void`	`reset()`	Resets the `count` field of this `ByteArrayOutputStream` to zero, so that all currently accumulated output in the output stream is discarded.
`int`	`size()`	Returns the current size of the buffer.
`byte[]`	`toByteArray()`	Creates a newly allocated byte array.
`String`	`toString()`	Converts the buffer's contents into a string decoding bytes using the default charset.
`String`	`toString(int hibyte)`	Deprecated. This method does not properly convert bytes into characters.
`String`	`toString(String charsetName)`	Converts the buffer's contents into a string by decoding the bytes using the named `charset`.
`String`	`toString(Charset charset)`	Converts the buffer's contents into a string by decoding the bytes using the specified `charset`.
`void`	`write(byte[] b, int off, int len)`	Writes `len` bytes from the specified byte array starting at offset `off` to this `ByteArrayOutputStream`.
`void`	`write(int b)`	Writes the specified byte to this `ByteArrayOutputStream`.
`void`	`writeBytes(byte[] b)`	Writes the complete contents of the specified byte array to this `ByteArrayOutputStream`.
`void`	`writeTo(OutputStream out)`	Writes the complete contents of this `ByteArrayOutputStream` to the specified output stream argument, as if by calling the output stream's write method using `out.write(buf, 0, count)`.

Methods declared in class java.io.OutputStream

flush, nullOutputStream, write

Methods declared in class java.lang.Object

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

Field Details

buf

protected byte[] buf

The buffer where data is stored.

count

protected int count

The number of valid bytes in the buffer.

Constructor Details

ByteArrayOutputStream

public ByteArrayOutputStream()

Creates a new ByteArrayOutputStream. The buffer capacity is initially 32 bytes, though its size increases if necessary.

ByteArrayOutputStream

public ByteArrayOutputStream(int size)

Creates a new ByteArrayOutputStream, with a buffer capacity of the specified size, in bytes.

Parameters:: size - the initial size.
Throws:: IllegalArgumentException - if size is negative.

Method Details

write

public void write(int b)

Writes the specified byte to this ByteArrayOutputStream.

Specified by:: write in class OutputStream
Parameters:: b - the byte to be written.

write

public void write(byte[] b, int off, int len)

Writes len bytes from the specified byte array starting at offset off to this ByteArrayOutputStream.

Overrides:: write in class OutputStream
Parameters:: b - the data.; off - the start offset in the data.; len - the number of bytes to write.
Throws:: NullPointerException - if b is null.; IndexOutOfBoundsException - if off is negative, len is negative, or len is greater than b.length - off

writeBytes

public void writeBytes(byte[] b)

Writes the complete contents of the specified byte array to this ByteArrayOutputStream.

API Note:: This method is equivalent to write(b, 0, b.length).
Parameters:: b - the data.
Throws:: NullPointerException - if b is null.
Since:: 11

writeTo

public void writeTo(OutputStream out) throws IOException

Writes the complete contents of this ByteArrayOutputStream to the specified output stream argument, as if by calling the output stream's write method using out.write(buf, 0, count).

Parameters:: out - the output stream to which to write the data.
Throws:: NullPointerException - if out is null.; IOException - if an I/O error occurs.

reset

public void reset()

Resets the count field of this ByteArrayOutputStream to zero, so that all currently accumulated output in the output stream is discarded. The output stream can be used again, reusing the already allocated buffer space.

See Also:

toByteArray

public byte[] toByteArray()

Creates a newly allocated byte array. Its size is the current size of this output stream and the valid contents of the buffer have been copied into it.

Returns:

the current contents of this output stream, as a byte array.

See Also:

size

public int size()

Returns the current size of the buffer.

Returns:

the value of the count field, which is the number of valid bytes in this output stream.

See Also:

toString

public String toString()

Converts the buffer's contents into a string decoding bytes using the default charset. The length of the new String is a function of the charset, and hence may not be equal to the size of the buffer.

This method always replaces malformed-input and unmappable-character sequences with the default replacement string for the default charset. The CharsetDecoder class should be used when more control over the decoding process is required.

Overrides:

toString in class Object

Returns:

String decoded from the buffer's contents.

Since:

1.1

See Also:

toString

public String toString(String charsetName) throws UnsupportedEncodingException

Converts the buffer's contents into a string by decoding the bytes using the named charset.

This method is equivalent to #toString(charset) that takes a charset.

An invocation of this method of the form

    ByteArrayOutputStream b;
    b.toString("UTF-8")

behaves in exactly the same way as the expression

    ByteArrayOutputStream b;
    b.toString(StandardCharsets.UTF_8)

Parameters:: charsetName - the name of a supported charset
Returns:: String decoded from the buffer's contents.
Throws:: UnsupportedEncodingException - If the named charset is not supported
Since:: 1.1

toString

public String toString(Charset charset)

Converts the buffer's contents into a string by decoding the bytes using the specified charset. The length of the new String is a function of the charset, and hence may not be equal to the length of the byte array.

This method always replaces malformed-input and unmappable-character sequences with the charset's default replacement string. The CharsetDecoder class should be used when more control over the decoding process is required.

Parameters:: charset - the charset to be used to decode the bytes
Returns:: String decoded from the buffer's contents.
Since:: 10

toString

@Deprecated public String toString(int hibyte)

Deprecated.

This method does not properly convert bytes into characters. As of JDK 1.1, the preferred way to do this is via the toString(String charsetName) or toString(Charset charset) method, which takes an encoding-name or charset argument, or the toString() method, which uses the default charset.

Creates a newly allocated string. Its size is the current size of the output stream and the valid contents of the buffer have been copied into it. Each character c in the resulting string is constructed from the corresponding element b in the byte array such that:

    c == (char)(((hibyte & 0xff) << 8) | (b & 0xff))

Parameters:

hibyte - the high byte of each resulting Unicode character.

Returns:

the current contents of the output stream, as a string.

See Also:

close

public void close() throws IOException

Closing a ByteArrayOutputStream has no effect. The methods in this class can be called after the stream has been closed without generating an IOException.

Specified by:: close in interface AutoCloseable
Specified by:: close in interface Closeable
Overrides:: close in class OutputStream
Throws:: IOException - if an I/O error occurs.

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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/io/ByteArrayOutputStream.html