# ByteArrayOutputStream
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
Summary:[Fields](https://developer.android.com/reference/java/io/ByteArrayOutputStream#lfields)\|[Ctors](https://developer.android.com/reference/java/io/ByteArrayOutputStream#pubctors)\|[Methods](https://developer.android.com/reference/java/io/ByteArrayOutputStream#pubmethods)\|[Inherited Methods](https://developer.android.com/reference/java/io/ByteArrayOutputStream#inhmethods)
# ByteArrayOutputStream
`
public
class
ByteArrayOutputStream
`
`
``
extends `[OutputStream](https://developer.android.com/reference/java/io/OutputStream)`
``
`
|---|---|-------------------------------|
| [java.lang.Object](https://developer.android.com/reference/java/lang/Object) |||
| ↳ | [java.io.OutputStream](https://developer.android.com/reference/java/io/OutputStream) ||
| | ↳ | java.io.ByteArrayOutputStream |
*** ** * ** ***
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`.
## Summary
| ### Fields ||
|---------------------|-------------------------------------------------------------------------------------------------------------------------------|
| ` protected byte[]` | [buf](https://developer.android.com/reference/java/io/ByteArrayOutputStream#buf) The buffer where data is stored. |
| ` protected int` | [count](https://developer.android.com/reference/java/io/ByteArrayOutputStream#count) The number of valid bytes in the buffer. |
| ### Public constructors ||
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---|
| ` `[ByteArrayOutputStream](https://developer.android.com/reference/java/io/ByteArrayOutputStream#ByteArrayOutputStream())`() ` Creates a new`ByteArrayOutputStream`. |
| ` `[ByteArrayOutputStream](https://developer.android.com/reference/java/io/ByteArrayOutputStream#ByteArrayOutputStream(int))`(int size) ` Creates a new`ByteArrayOutputStream`, with a buffer capacity of the specified size, in bytes. |
| ### Public methods ||
|-----------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| ` void` | ` `[close](https://developer.android.com/reference/java/io/ByteArrayOutputStream#close())`() ` Closing a`ByteArrayOutputStream`has no effect. |
| ` void` | ` `[reset](https://developer.android.com/reference/java/io/ByteArrayOutputStream#reset())`() ` Resets the`count`field of this`ByteArrayOutputStream`to zero, so that all currently accumulated output in the output stream is discarded. |
| ` int` | ` `[size](https://developer.android.com/reference/java/io/ByteArrayOutputStream#size())`() ` Returns the current size of the buffer. |
| ` byte[]` | ` `[toByteArray](https://developer.android.com/reference/java/io/ByteArrayOutputStream#toByteArray())`() ` Creates a newly allocated byte array. |
| ` `[String](https://developer.android.com/reference/java/lang/String) | ` `[toString](https://developer.android.com/reference/java/io/ByteArrayOutputStream#toString(java.lang.String))`(`[String](https://developer.android.com/reference/java/lang/String)` charsetName) ` Converts the buffer's contents into a string by decoding the bytes using the named[charset](https://developer.android.com/reference/java/nio/charset/Charset). |
| ` `[String](https://developer.android.com/reference/java/lang/String) | ` `[toString](https://developer.android.com/reference/java/io/ByteArrayOutputStream#toString(java.nio.charset.Charset))`(`[Charset](https://developer.android.com/reference/java/nio/charset/Charset)` charset) ` Converts the buffer's contents into a string by decoding the bytes using the specified[charset](https://developer.android.com/reference/java/nio/charset/Charset). |
| ` `[String](https://developer.android.com/reference/java/lang/String) | ` `[toString](https://developer.android.com/reference/java/io/ByteArrayOutputStream#toString())`() ` Converts the buffer's contents into a string decoding bytes using the platform's default character set. |
| ` `[String](https://developer.android.com/reference/java/lang/String) | ` `[toString](https://developer.android.com/reference/java/io/ByteArrayOutputStream#toString(int))`(int hibyte) ` *This method was deprecated in API level 15. This method does not properly convert bytes into characters. As of JDK 1.1, the preferred way to do this is via the[toString(java.lang.String)](https://developer.android.com/reference/java/io/ByteArrayOutputStream#toString(java.lang.String))or[toString(java.nio.charset.Charset)](https://developer.android.com/reference/java/io/ByteArrayOutputStream#toString(java.nio.charset.Charset))method, which takes an encoding-name or charset argument, or the`toString()`method, which uses the platform's default character encoding.* |
| ` void` | ` `[write](https://developer.android.com/reference/java/io/ByteArrayOutputStream#write(byte[],%20int,%20int))`(byte[] b, int off, int len) ` Writes`len`bytes from the specified byte array starting at offset`off`to this`ByteArrayOutputStream`. |
| ` void` | ` `[write](https://developer.android.com/reference/java/io/ByteArrayOutputStream#write(int))`(int b) ` Writes the specified byte to this`ByteArrayOutputStream`. |
| ` void` | ` `[writeBytes](https://developer.android.com/reference/java/io/ByteArrayOutputStream#writeBytes(byte[]))`(byte[] b) ` Writes the complete contents of the specified byte array to this`ByteArrayOutputStream`. |
| ` void` | ` `[writeTo](https://developer.android.com/reference/java/io/ByteArrayOutputStream#writeTo(java.io.OutputStream))`(`[OutputStream](https://developer.android.com/reference/java/io/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)`. |
| ### Inherited methods |
|-----------------------|---|
| From class` `[java.io.OutputStream](https://developer.android.com/reference/java/io/OutputStream)` ` |----------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | ` void` | ` `[close](https://developer.android.com/reference/java/io/OutputStream#close())`() ` Closes this output stream and releases any system resources associated with this stream. | | ` void` | ` `[flush](https://developer.android.com/reference/java/io/OutputStream#flush())`() ` Flushes this output stream and forces any buffered output bytes to be written out. | | ` static `[OutputStream](https://developer.android.com/reference/java/io/OutputStream) | ` `[nullOutputStream](https://developer.android.com/reference/java/io/OutputStream#nullOutputStream())`() ` Returns a new`OutputStream`which discards all bytes. | | ` void` | ` `[write](https://developer.android.com/reference/java/io/OutputStream#write(byte[]))`(byte[] b) ` Writes`b.length`bytes from the specified byte array to this output stream. | | ` void` | ` `[write](https://developer.android.com/reference/java/io/OutputStream#write(byte[],%20int,%20int))`(byte[] b, int off, int len) ` Writes`len`bytes from the specified byte array starting at offset`off`to this output stream. | | ` abstract void` | ` `[write](https://developer.android.com/reference/java/io/OutputStream#write(int))`(int b) ` Writes the specified byte to this output stream. | ||
| From class` `[java.lang.Object](https://developer.android.com/reference/java/lang/Object)` ` |--------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | ` `[Object](https://developer.android.com/reference/java/lang/Object) | ` `[clone](https://developer.android.com/reference/java/lang/Object#clone())`() ` Creates and returns a copy of this object. | | ` boolean` | ` `[equals](https://developer.android.com/reference/java/lang/Object#equals(java.lang.Object))`(`[Object](https://developer.android.com/reference/java/lang/Object)` obj) ` Indicates whether some other object is "equal to" this one. | | ` void` | ` `[finalize](https://developer.android.com/reference/java/lang/Object#finalize())`() ` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. | | ` final `[Class](https://developer.android.com/reference/java/lang/Class)`` | ` `[getClass](https://developer.android.com/reference/java/lang/Object#getClass())`() ` Returns the runtime class of this`Object`. | | ` int` | ` `[hashCode](https://developer.android.com/reference/java/lang/Object#hashCode())`() ` Returns a hash code value for the object. | | ` final void` | ` `[notify](https://developer.android.com/reference/java/lang/Object#notify())`() ` Wakes up a single thread that is waiting on this object's monitor. | | ` final void` | ` `[notifyAll](https://developer.android.com/reference/java/lang/Object#notifyAll())`() ` Wakes up all threads that are waiting on this object's monitor. | | ` `[String](https://developer.android.com/reference/java/lang/String) | ` `[toString](https://developer.android.com/reference/java/lang/Object#toString())`() ` Returns a string representation of the object. | | ` final void` | ` `[wait](https://developer.android.com/reference/java/lang/Object#wait(long,%20int))`(long timeoutMillis, int nanos) ` Causes the current thread to wait until it is awakened, typically by being*notified* or*interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` `[wait](https://developer.android.com/reference/java/lang/Object#wait(long))`(long timeoutMillis) ` Causes the current thread to wait until it is awakened, typically by being*notified* or*interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` `[wait](https://developer.android.com/reference/java/lang/Object#wait())`() ` Causes the current thread to wait until it is awakened, typically by being*notified* or*interrupted*. | ||
| From interface` `[java.io.Closeable](https://developer.android.com/reference/java/io/Closeable)` ` |------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------| | ` abstract void` | ` `[close](https://developer.android.com/reference/java/io/Closeable#close())`() ` Closes this stream and releases any system resources associated with it. | ||
| From interface` `[java.io.Flushable](https://developer.android.com/reference/java/io/Flushable)` ` |------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------| | ` abstract void` | ` `[flush](https://developer.android.com/reference/java/io/Flushable#flush())`() ` Flushes this stream by writing any buffered output to the underlying stream. | ||
| From interface` `[java.lang.AutoCloseable](https://developer.android.com/reference/java/lang/AutoCloseable)` ` |------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------| | ` abstract void` | ` `[close](https://developer.android.com/reference/java/lang/AutoCloseable#close())`() ` Closes this resource, relinquishing any underlying resources. | ||
## Fields
### buf
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
protected byte[] buf
```
The buffer where data is stored.
### count
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
protected int count
```
The number of valid bytes in the buffer.
## Public constructors
### ByteArrayOutputStream
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public ByteArrayOutputStream ()
```
Creates a new`ByteArrayOutputStream`. The buffer capacity is initially 32 bytes, though its size increases if necessary.
### ByteArrayOutputStream
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public ByteArrayOutputStream (int size)
```
Creates a new`ByteArrayOutputStream`, with a buffer capacity of the specified size, in bytes.
| Parameters ||
|--------|---------------------------------|
| `size` | `int`: the initial size.
|
| Throws ||
|--------------------------------------------------------------------------------------------------------|----------------------|
| [IllegalArgumentException](https://developer.android.com/reference/java/lang/IllegalArgumentException) | if size is negative. |
## Public methods
### close
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public void close ()
```
Closing a`ByteArrayOutputStream`has no effect. The methods in this class can be called after the stream has been closed without generating an`IOException`.
| Throws ||
|----------------------------------------------------------------------------|---|
| [IOException](https://developer.android.com/reference/java/io/IOException) | |
### reset
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
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:**
- [ByteArrayInputStream.count](https://developer.android.com/reference/java/io/ByteArrayInputStream#count)
### size
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public int size ()
```
Returns the current size of the buffer.
| Returns ||
|-------|------------------------------------------------------------------------------------------------|
| `int` | the value of the`count`field, which is the number of valid bytes in this output stream.
|
**See also:**
- [count](https://developer.android.com/reference/java/io/ByteArrayOutputStream#count)
### toByteArray
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
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 ||
|----------|---------------------------------------------------------------------|
| `byte[]` | the current contents of this output stream, as a byte array.
|
**See also:**
- [size()](https://developer.android.com/reference/java/io/ByteArrayOutputStream#size())
### toString
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public String toString (String charsetName)
```
Converts the buffer's contents into a string by decoding the bytes using the named[charset](https://developer.android.com/reference/java/nio/charset/Charset).
This method is equivalent to`#toString(charset)`that takes a[charset](https://developer.android.com/reference/java/nio/charset/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` | `String`: the name of a supported[charset](https://developer.android.com/reference/java/nio/charset/Charset)
|
| Returns ||
|--------------------------------------------------------------------|---------------------------------------------------|
| [String](https://developer.android.com/reference/java/lang/String) | String decoded from the buffer's contents.
|
| Throws ||
|--------------------------------------------------------------------------------------------------------------|---------------------------------------|
| [UnsupportedEncodingException](https://developer.android.com/reference/java/io/UnsupportedEncodingException) | If the named charset is not supported |
### toString
Added in[API level 33](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public String toString (Charset charset)
```
Converts the buffer's contents into a string by decoding the bytes using the specified[charset](https://developer.android.com/reference/java/nio/charset/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](https://developer.android.com/reference/java/nio/charset/CharsetDecoder)class should be used when more control over the decoding process is required.
| Parameters ||
|-----------|---------------------------------------------------------------------------------------------------------------------------------|
| `charset` | `Charset`: the[charset](https://developer.android.com/reference/java/nio/charset/Charset)to be used to decode the`bytes`
|
| Returns ||
|--------------------------------------------------------------------|---------------------------------------------------|
| [String](https://developer.android.com/reference/java/lang/String) | String decoded from the buffer's contents.
|
### toString
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public String toString ()
```
Converts the buffer's contents into a string decoding bytes using the platform's default character set. The length of the new`String`is a function of the character set, 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 platform's default character set. The[CharsetDecoder](https://developer.android.com/reference/java/nio/charset/CharsetDecoder)class should be used when more control over the decoding process is required.
| Returns ||
|--------------------------------------------------------------------|---------------------------------------------------|
| [String](https://developer.android.com/reference/java/lang/String) | String decoded from the buffer's contents.
|
### toString
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
Deprecated in[API level 15](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public String toString (int hibyte)
```
**This method was deprecated in API level 15.**
This method does not properly convert bytes into characters. As of JDK 1.1, the preferred way to do this is via the[toString(java.lang.String)](https://developer.android.com/reference/java/io/ByteArrayOutputStream#toString(java.lang.String))or[toString(java.nio.charset.Charset)](https://developer.android.com/reference/java/io/ByteArrayOutputStream#toString(java.nio.charset.Charset))method, which takes an encoding-name or charset argument, or the`toString()`method, which uses the platform's default character encoding.
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` | `int`: the high byte of each resulting Unicode character.
|
| Returns ||
|--------------------------------------------------------------------|----------------------------------------------------------------|
| [String](https://developer.android.com/reference/java/lang/String) | the current contents of the output stream, as a string.
|
**See also:**
- [size()](https://developer.android.com/reference/java/io/ByteArrayOutputStream#size())
- [toString(String)](https://developer.android.com/reference/java/io/ByteArrayOutputStream#toString(java.lang.String))
- [toString()](https://developer.android.com/reference/java/io/ByteArrayOutputStream#toString())
### write
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public void write (byte[] b,
int off,
int len)
```
Writes`len`bytes from the specified byte array starting at offset`off`to this`ByteArrayOutputStream`.
| Parameters ||
|-------|---------------------------------------------|
| `b` | `byte`: the data.
|
| `off` | `int`: the start offset in the data.
|
| `len` | `int`: the number of bytes to write.
|
| Throws ||
|----------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------|
| [NullPointerException](https://developer.android.com/reference/java/lang/NullPointerException) | if`b`is`null`. |
| [IndexOutOfBoundsException](https://developer.android.com/reference/java/lang/IndexOutOfBoundsException) | if`off`is negative,`len`is negative, or`len`is greater than`b.length - off` |
### write
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public void write (int b)
```
Writes the specified byte to this`ByteArrayOutputStream`.
| Parameters ||
|-----|---------------------------------------|
| `b` | `int`: the byte to be written.
|
### writeBytes
Added in[API level 33](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
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)](https://developer.android.com/reference/java/io/ByteArrayOutputStream#write(byte[],%20int,%20int)).
| Parameters ||
|-----|--------------------------|
| `b` | `byte`: the data.
|
| Throws ||
|------------------------------------------------------------------------------------------------|----------------|
| [NullPointerException](https://developer.android.com/reference/java/lang/NullPointerException) | if`b`is`null`. |
### writeTo
Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)
```
public 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)`.
| Parameters ||
|-------|----------------------------------------------------------------------|
| `out` | `OutputStream`: the output stream to which to write the data.
|
| Throws ||
|------------------------------------------------------------------------------------------------|-------------------------|
| [NullPointerException](https://developer.android.com/reference/java/lang/NullPointerException) | if`out`is`null`. |
| [IOException](https://developer.android.com/reference/java/io/IOException) | if an I/O error occurs. |