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You cannot assume that any given stream reading call will fill the byte[] passed in to the method. Instead, you must check the value returned by the read method to see how many bytes were read. Fail to do so, and you introduce bug that is both harmful and difficult to reproduce.

Similarly, you cannot assume that InputStream.skip will actually skip the requested number of bytes, but must check the value returned from the method.

This rule raises an issue when an InputStream.read method that accepts a byte[] is called, but the return value is not checked, and when the return value of InputStream.skip is not checked. The rule also applies to InputStream child classes.

Noncompliant Code Example

public void doSomething(String fileName) {
  try {
    InputStream is = new InputStream(file);
    byte [] buffer = new byte[1000];
    is.read(buffer);  // Noncompliant
    // ...
  } catch (IOException e) { ... }
}


Compliant Solution

public void doSomething(String fileName) {
  try {
    InputStream is = new InputStream(file);
    byte [] buffer = new byte[1000];
    int count = 0;
    while (count = is.read(buffer) > 0) {
      // ...
    }
  } catch (IOException e) { ... }
}