Suspicious byte value returned from 'InputStream.read()'

Reports expressions of byte type returned from a method implementing the InputStream.read() method.

This is suspicious because InputStream.read() should return a value in the range from 0 to 255, while an expression of byte type contains a value from -128 to 127. The quick-fix converts the expression into an unsigned byte by applying the bitmask 0xFF.

Example:

class MyInputStream extends InputStream {
  int pos = 0;
  byte[] data;

  MyInputStream(byte[] input) {
    data = input;
  }

  @Override
  public int read() {
    if (pos == data.length) {
      return -1;
    }
    return data[pos++]; // problem
  }
}

After applying the quick-fix:

class MyInputStream extends InputStream {
  int pos = 0;
  byte[] data;

  MyInputStream(byte[] input) {
    data = input;
  }

  @Override
  public int read() {
    if (pos == data.length) {
      return -1;
    }
    return data[pos++] & 0xFF;
  }
}

Locating this inspection

By ID

Can be used to locate inspection in e.g. Qodana configuration files, where you can quickly enable or disable it, or adjust its settings.

SuspiciousReturnByteInputStream

Via Settings dialog

Path to the inspection settings via IntelliJ Platform IDE Settings dialog, when you need to adjust inspection settings directly from your IDE.

Settings or Preferences | Editor | Inspections | Java | Probable bugs

New in 2023.2

Suppressing Inspection

You can suppress this inspection by placing the following comment marker before the code fragment where you no longer want messages from this inspection to appear:

//noinspection SuspiciousReturnByteInputStream

More detailed instructions as well as other ways and options that you have can be found in the product documentation:

IntelliJ IDEA 2025.2

Inspection Details
By default bundled with:	IntelliJ IDEA 2025.2, Qodana for JVM 2025.2,

Last modified: 18 September 2025