Is BufferedWriter.append in Java thread safe?

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So I have a file that multiple threads try to write to simultaneously.

I used Buffered Writer to write to the file. Now, my question is if use append to append thread's content to the file, will it be thread safe?

asked Nov 13 '18 at 21:18

Aditya

5321622

Are they all using the same writer?

– shmosel
Nov 13 '18 at 21:19

1

@MadProgrammer but that isn't a documented property, so it would be inadvisable to rely on it.

– Andy Turner
Nov 13 '18 at 21:29

1

@AndyTurner the superclass Writer's javadoc language indicates the subclasses need to synchronize on the object lock to protect their critical sessions. Could have been more explicit, but it's there

– Erwin Bolwidt
Nov 13 '18 at 21:33

1

@ErwinBolwidt true, but it doesn't define what the critical sections are.

– Andy Turner
Nov 13 '18 at 21:34

1

@AndyTurner I guess it comes down to the definition of "critical sections". Perhaps raise a change request to have the documentation more clearly defined :/

– MadProgrammer
Nov 13 '18 at 21:38

|
show 4 more comments

So I have a file that multiple threads try to write to simultaneously.

I used Buffered Writer to write to the file. Now, my question is if use append to append thread's content to the file, will it be thread safe?

asked Nov 13 '18 at 21:18

Aditya

5321622

Are they all using the same writer?

– shmosel
Nov 13 '18 at 21:19

1

@MadProgrammer but that isn't a documented property, so it would be inadvisable to rely on it.

– Andy Turner
Nov 13 '18 at 21:29

1

@AndyTurner the superclass Writer's javadoc language indicates the subclasses need to synchronize on the object lock to protect their critical sessions. Could have been more explicit, but it's there

– Erwin Bolwidt
Nov 13 '18 at 21:33

1

@ErwinBolwidt true, but it doesn't define what the critical sections are.

– Andy Turner
Nov 13 '18 at 21:34

1

@AndyTurner I guess it comes down to the definition of "critical sections". Perhaps raise a change request to have the documentation more clearly defined :/

– MadProgrammer
Nov 13 '18 at 21:38

|
show 4 more comments

So I have a file that multiple threads try to write to simultaneously.

I used Buffered Writer to write to the file. Now, my question is if use append to append thread's content to the file, will it be thread safe?

asked Nov 13 '18 at 21:18

Aditya

5321622

So I have a file that multiple threads try to write to simultaneously.

I used Buffered Writer to write to the file. Now, my question is if use append to append thread's content to the file, will it be thread safe?

java processbuilder

asked Nov 13 '18 at 21:18

Aditya

5321622

asked Nov 13 '18 at 21:18

Aditya

5321622

asked Nov 13 '18 at 21:18

Aditya

5321622

asked Nov 13 '18 at 21:18

Aditya

5321622

asked Nov 13 '18 at 21:18

Aditya

5321622

Are they all using the same writer?

– shmosel
Nov 13 '18 at 21:19

1

@MadProgrammer but that isn't a documented property, so it would be inadvisable to rely on it.

– Andy Turner
Nov 13 '18 at 21:29

1

@AndyTurner the superclass Writer's javadoc language indicates the subclasses need to synchronize on the object lock to protect their critical sessions. Could have been more explicit, but it's there

– Erwin Bolwidt
Nov 13 '18 at 21:33

1

@ErwinBolwidt true, but it doesn't define what the critical sections are.

– Andy Turner
Nov 13 '18 at 21:34

1

@AndyTurner I guess it comes down to the definition of "critical sections". Perhaps raise a change request to have the documentation more clearly defined :/

– MadProgrammer
Nov 13 '18 at 21:38

|
show 4 more comments

Are they all using the same writer?

– shmosel
Nov 13 '18 at 21:19

1

@MadProgrammer but that isn't a documented property, so it would be inadvisable to rely on it.

– Andy Turner
Nov 13 '18 at 21:29

1

@AndyTurner the superclass Writer's javadoc language indicates the subclasses need to synchronize on the object lock to protect their critical sessions. Could have been more explicit, but it's there

– Erwin Bolwidt
Nov 13 '18 at 21:33

1

@ErwinBolwidt true, but it doesn't define what the critical sections are.

– Andy Turner
Nov 13 '18 at 21:34

1

@AndyTurner I guess it comes down to the definition of "critical sections". Perhaps raise a change request to have the documentation more clearly defined :/

– MadProgrammer
Nov 13 '18 at 21:38

Are they all using the same writer?

– shmosel
Nov 13 '18 at 21:19

@MadProgrammer but that isn't a documented property, so it would be inadvisable to rely on it.

– Andy Turner
Nov 13 '18 at 21:29

@AndyTurner the superclass Writer's javadoc language indicates the subclasses need to synchronize on the object lock to protect their critical sessions. Could have been more explicit, but it's there

– Erwin Bolwidt
Nov 13 '18 at 21:33

@ErwinBolwidt true, but it doesn't define what the critical sections are.

– Andy Turner
Nov 13 '18 at 21:34

@AndyTurner I guess it comes down to the definition of "critical sections". Perhaps raise a change request to have the documentation more clearly defined :/

– MadProgrammer
Nov 13 '18 at 21:38

|
show 4 more comments

2 Answers
2

active

oldest

votes

When you inspect the implementation, you can see that there is a lock object and the methods such as write or flush are synchronizing with a common object lock.

synchronized (lock) 
 ... here is the body of the method, enclosed in the sync block

answered Nov 13 '18 at 21:33

Donat

848128

add a comment |

One of the problems with the question "is it thread safe" is that the answer depends upon what you mean by thread safety.

A class can be thread safe, in the sense that its own invariants cannot be broken by its use by multiple threads simultaneously; but you can still use that class in a non-threadsafe way.

For example:

void write(int a, String blah) 
 writer.write(a);
 writer.write(blah);

These two writes are not performed atomically, so there is a possibility that the writes from two threads interleave.

If you are in any doubt about thread safety, manage it yourself.

answered Nov 13 '18 at 21:40

Andy Turner

84.4k983144

I think it's fairly obvious from my question, that I am not asking about chaining together multiple appends or asking about a situation where I deliberately try to break the thread safety of the append method(if it was thread safe). I have described my use case in the question.

– Aditya
Nov 15 '18 at 15:55

add a comment |

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2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

When you inspect the implementation, you can see that there is a lock object and the methods such as write or flush are synchronizing with a common object lock.

synchronized (lock) 
 ... here is the body of the method, enclosed in the sync block

answered Nov 13 '18 at 21:33

Donat

848128

add a comment |

When you inspect the implementation, you can see that there is a lock object and the methods such as write or flush are synchronizing with a common object lock.

synchronized (lock) 
 ... here is the body of the method, enclosed in the sync block

answered Nov 13 '18 at 21:33

Donat

848128

add a comment |

When you inspect the implementation, you can see that there is a lock object and the methods such as write or flush are synchronizing with a common object lock.

synchronized (lock) 
 ... here is the body of the method, enclosed in the sync block

answered Nov 13 '18 at 21:33

Donat

848128

When you inspect the implementation, you can see that there is a lock object and the methods such as write or flush are synchronizing with a common object lock.

synchronized (lock) 
 ... here is the body of the method, enclosed in the sync block

answered Nov 13 '18 at 21:33

Donat

848128

answered Nov 13 '18 at 21:33

Donat

848128

answered Nov 13 '18 at 21:33

Donat

848128

answered Nov 13 '18 at 21:33

Donat

848128

add a comment |

One of the problems with the question "is it thread safe" is that the answer depends upon what you mean by thread safety.

A class can be thread safe, in the sense that its own invariants cannot be broken by its use by multiple threads simultaneously; but you can still use that class in a non-threadsafe way.

For example:

void write(int a, String blah) 
 writer.write(a);
 writer.write(blah);

These two writes are not performed atomically, so there is a possibility that the writes from two threads interleave.

If you are in any doubt about thread safety, manage it yourself.

answered Nov 13 '18 at 21:40

Andy Turner

84.4k983144

I think it's fairly obvious from my question, that I am not asking about chaining together multiple appends or asking about a situation where I deliberately try to break the thread safety of the append method(if it was thread safe). I have described my use case in the question.

– Aditya
Nov 15 '18 at 15:55

add a comment |

One of the problems with the question "is it thread safe" is that the answer depends upon what you mean by thread safety.

A class can be thread safe, in the sense that its own invariants cannot be broken by its use by multiple threads simultaneously; but you can still use that class in a non-threadsafe way.

For example:

void write(int a, String blah) 
 writer.write(a);
 writer.write(blah);

These two writes are not performed atomically, so there is a possibility that the writes from two threads interleave.

If you are in any doubt about thread safety, manage it yourself.

answered Nov 13 '18 at 21:40

Andy Turner

84.4k983144

I think it's fairly obvious from my question, that I am not asking about chaining together multiple appends or asking about a situation where I deliberately try to break the thread safety of the append method(if it was thread safe). I have described my use case in the question.

– Aditya
Nov 15 '18 at 15:55

add a comment |

One of the problems with the question "is it thread safe" is that the answer depends upon what you mean by thread safety.

A class can be thread safe, in the sense that its own invariants cannot be broken by its use by multiple threads simultaneously; but you can still use that class in a non-threadsafe way.

For example:

void write(int a, String blah) 
 writer.write(a);
 writer.write(blah);

These two writes are not performed atomically, so there is a possibility that the writes from two threads interleave.

If you are in any doubt about thread safety, manage it yourself.

answered Nov 13 '18 at 21:40

Andy Turner

84.4k983144

One of the problems with the question "is it thread safe" is that the answer depends upon what you mean by thread safety.

A class can be thread safe, in the sense that its own invariants cannot be broken by its use by multiple threads simultaneously; but you can still use that class in a non-threadsafe way.

For example:

void write(int a, String blah) 
 writer.write(a);
 writer.write(blah);

These two writes are not performed atomically, so there is a possibility that the writes from two threads interleave.

If you are in any doubt about thread safety, manage it yourself.

answered Nov 13 '18 at 21:40

Andy Turner

84.4k983144

answered Nov 13 '18 at 21:40

Andy Turner

84.4k983144

answered Nov 13 '18 at 21:40

Andy Turner

84.4k983144

answered Nov 13 '18 at 21:40

Andy Turner

84.4k983144

I think it's fairly obvious from my question, that I am not asking about chaining together multiple appends or asking about a situation where I deliberately try to break the thread safety of the append method(if it was thread safe). I have described my use case in the question.

– Aditya
Nov 15 '18 at 15:55

add a comment |

I think it's fairly obvious from my question, that I am not asking about chaining together multiple appends or asking about a situation where I deliberately try to break the thread safety of the append method(if it was thread safe). I have described my use case in the question.

– Aditya
Nov 15 '18 at 15:55

I think it's fairly obvious from my question, that I am not asking about chaining together multiple appends or asking about a situation where I deliberately try to break the thread safety of the append method(if it was thread safe). I have described my use case in the question.

– Aditya
Nov 15 '18 at 15:55

add a comment |

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