Why toString() on an Object instance (which is null) is not throwing NPE?

Question

Consider below one :

Object nothingToHold = null;

System.out.println(nothingToHold);  //  Safely prints \'null\'

Here, Sysout must be expe

Answer 1

PrintWriter's println(Object) (which is the method called when you write System.out.println(nothingToHold)) calls String.valueOf(x) as explained in the Javadoc:

/**
 * Prints an Object and then terminates the line.  This method calls
 * at first String.valueOf(x) to get the printed object's string value,
 * then behaves as
 * though it invokes {@link #print(String)} and then
 * {@link #println()}.
 *
 * @param x  The Object to be printed.
 */
public void println(Object x)

String.valueOf(Object) converts the null to "null":

/**
 * Returns the string representation of the Object argument.
 *
 * @param   obj   an Object.
 * @return  if the argument is null, then a string equal to
 *          "null"; otherwise, the value of
 *          obj.toString() is returned.
 * @see     java.lang.Object#toString()
 */
public static String valueOf(Object obj)