Does Java’s Try-catch-Resources flush automatically?

Question

When using an object of the type FileInputStream and FileOutputStream within a Try-catch-Resources java automatically uses the close-up() in the end, but, and the flush() is automatic or not?

// Exemplo
try(FileOutputStream fos = new FileOutputStream("arquivo.txt")){
    try (BufferedOutputStream bos = new BufferedOutputStream(fos)) {
        bos.write("Teste");
        bos.flush(); // Precisa usar o flush()
    }
    fos.flush(); // Precisa usar o flush()
}

Answer 1

Whether or not the flush is automatic depends on the implementation of the concrete class you use.

Try with Resources expects only Closeable or Autocloseable objects, it is not directly connected to the flush, however some implementations of these interfaces run the flush before the close.

https://stackoverflow.com/questions/32324492/is-flush-call-necessary-when-using-try-with-resources