SystemConsoleNull
System.console() no longer returns null in JDK 22 and newer versions

The problem

Null-checking System.console() is not a reliable way to detect if the console is connected to a terminal.

See JDK 22 Release Note: JLine As The Default Console Provider:

System.console() now returns a Console object when the standard streams are redirected or connected to a virtual terminal. In prior releases, System.console() returned null for these cases. This change may impact code that uses the return from System.console() to test if the VM is connected to a terminal. If needed, running with -Djdk.console=java.base will restore older behavior where the console is only returned when it is connected to a terminal.

A new method Console.isTerminal() has been added to test if console is connected to a terminal.

and JDK 25 release note Release Note: Default Console Implementation No Longer Based On JLine:

The default Console obtained via System.console() is no longer based on JLine. Since JDK 20, the JDK has included a JLine-based Console implementation, offering a richer user experience and better support for virtual terminal environments, such as IDEs. This implementation was initially opt-in via a system property in JDK 20 and JDK 21 and became the default in JDK 22. However, maintaining the JLine-based Console proved challenging. As a result, in JDK 25, it has reverted to being opt-in, as it was in JDK 20 and JDK 21.

To prepare for this change while remaining compatible with JDK versions prior to JDK 22, consider using reflection to call Console#isTerminal on JDK versions that support it:

  @SuppressWarnings("SystemConsoleNull") // https://errorprone.info/bugpattern/SystemConsoleNull
  private static boolean systemConsoleIsTerminal() {
    Console systemConsole = System.console();
    if (Runtime.version().feature() < 22 || systemConsole == null) {
      return systemConsole != null;
    }
    try {
      return (Boolean) Console.class.getMethod("isTerminal").invoke(systemConsole);
    } catch (ReflectiveOperationException e) {
      throw new LinkageError(e.getMessage(), e);
    }
  }

Suppression

Suppress false positives by adding the suppression annotation @SuppressWarnings("SystemConsoleNull") to the enclosing element.