Are the Java console streams subclasses of System?
System.out is a static variable of the System class that holds a reference to a PrintStream used to channel output to the host system’s console. System.err is also a PrintStream and System.in is an InputStream. When the Java runtime system starts up it automatically hooks-up these object references to the host system’s output, error and input streams. The PrintStream and InputStream types used to interface with the host system are not subclasses of the System class, they are a subclasses of the java.io.OutputStream and InputStream hierarchy. Notably the PrintStream class never throws IOException, though you can use the checkError() method to discover any problems. The common technique of making print calls with System.out.println() gives the impression that println() may be a method of the System class but it is not, it is a method of the PrintStream class. Actions: Follow-up, clarify or correct this answer. Submit a new question.
System.out is a static variable of the System class that holds a reference to a PrintStream used to channel output to the host system’s console. System.err is also a PrintStream and System.in is an InputStream. When the Java runtime system starts up it automatically hooks-up these object references to the host system’s output, error and input streams. The PrintStream and InputStream types used to interface with the host system are not subclasses of the System class, they are a subclasses of the java.io.OutputStream and InputStream hierarchy. Notably the PrintStream class never throws IOException, though you can use the checkError() method to discover any problems. The common technique of making print calls with System.out.println() gives the impression that println() may be a method of the System class but it is not, it is a method of the PrintStream class. Actions: Follow-up or correct this answer. Submit a new question.
