More Library Puzzlers - Java Puzzlers: Traps, Pitfalls, and Corner Cases - page 245

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Puzzle 80: Further Reflection
This program produces its output by printing an object that is created reflectively. What does the
program print?
public class Outer {
public static void main(String[] args) throws Exception {
new Outer().greetWorld();
}
private void greetWorld() throws Exception {
System.out.println(Inner.class.newInstance());
}
public class Inner {
public String toString() {
return "Hello world";
}
}
}
Solution 80: Further Reflection
This program looks like yet another unusual variant on the usual Hello world program. The main
method in Outer creates an Outer instance and calls its greetWorld method, which prints the string
form of a new Inner instance that it creates reflectively. The toString method of Inner always
returns the standard greeting, so the output of the program should, as usual, be Hello world . If you
try running it, you'll find the actual output to be longer and more confusing: