java.io · java.base · since Java 1.0

InputStream

declaration

public abstract class InputStream implements Closeable

The abstract byte source: read() returns 0–255 or −1 at end. Everything binary flows through it, usually wrapped in a BufferedInputStream.

Key methods

`int read()`	One byte (as int) or −1 at end of stream.
`int read(byte[] b)`	May fill FEWER bytes than requested — loop or use readNBytes.
`byte[] readAllBytes()`	Slurp the rest (small payloads).
`long transferTo(OutputStream out)`	Pipe everything downstream (Java 9).
`static InputStream nullInputStream()`	An empty stream for tests/defaults.