Java Puzzles: exceptional puzzlers

public class Indecisive { 
    public static void main(String[] args) {
        System.out.println(decision());
    }

    static boolean decision() {
        try {
            return true;
        } finally {
            return false;
        }
    } 
}

import java.io.IOException;

public class Arcane1 {
    public static void main(String[] args) {
        try {
            System.out.println("Hello world");
        } catch(IOException e) {
            System.out.println("I've never seen println fail!");
        }
    }
}

public class Arcane2 {
    public static void main(String[] args) {
        try {
            // If you have nothing nice to say, say nothing
        } catch(Exception e) {
            System.out.println("This can't happen");
        }
    }
}

interface Type1 {
    void f() throws CloneNotSupportedException;
}

interface Type2 {
    void f() throws InterruptedException;
}

interface Type3 extends Type1, Type2 {
}

public class Arcane3 implements Type3 {
    public void f() {
        System.out.println("Hello world");
    }

    public static void main(String[] args) {
        Type3 t3 = new Arcane3();
        t3.f();
    }
}

public class UnwelcomeGuest {
    public static final long GUEST_USER_ID = -1;

    private static final long USER_ID;
    static {
        try {
            USER_ID = getUserIdFromEnvironment();
        } catch (IdUnavailableException e) {
            USER_ID = GUEST_USER_ID;
            System.out.println("Logging in as guest");
        }
    }

    private static long getUserIdFromEnvironment() 
            throws IdUnavailableException { 
        throw new IdUnavailableException(); // Simulate an error
    }

    public static void main(String[] args) {
        System.out.println("User ID: " + USER_ID);
    }
}

class IdUnavailableException extends Exception { 
}

public class HelloGoodbye {
    public static void main(String[] args) {
        try {
            System.out.println("Hello world");
            System.exit(0);
        } finally {
            System.out.println("Goodbye world");
        }
    } 
}

public class Reluctant {
    private Reluctant internalInstance = new Reluctant();

    public Reluctant() throws Exception {
        throw new Exception("I'm not coming out");
    }

    public static void main(String[] args) {
        try {
            Reluctant b = new Reluctant();
            System.out.println("Surprise!");
        } catch (Exception ex) {
            System.out.println("I told you so");
        }
    }
}

import java.io.*;

public class Copy {
    static void copy(String src, String dest) throws IOException {
        InputStream in = null;
        OutputStream out = null;
        try {
            in = new FileInputStream(src);
            out = new FileOutputStream(dest);
            byte[] buf = new byte[1024];
            int n;
            while ((n = in.read(buf)) > 0)
                out.write(buf, 0, n);
        } finally {
            if (in != null) in.close();
            if (out != null) out.close();
        } 
    }

    public static void main(String[] args) throws IOException {
        if (args.length != 2)
            System.out.println("Usage: java Copy  ");
        else
            copy(args[0], args[1]);
    }
}

public class Loop {
    public static void main(String[] args) {
        int[][] tests = { { 6, 5, 4, 3, 2, 1 }, { 1, 2 },
                          { 1, 2, 3 }, { 1, 2, 3, 4 }, { 1 } };
        int n = 0;

        try {
            int i = 0;
            while (true) {
                if (thirdElementIsThree(tests[i++]))
                    n++;
            }
        } catch(ArrayIndexOutOfBoundsException e) {
            // No more tests to process
        }
        System.out.println(n);
    }

    private static boolean thirdElementIsThree(int[] a) {
        return a.length >= 3 & a[2] == 3;
    }
}

public class Thrower {
    public static void main(String[] args) {
        sneakyThrow(new Exception("This is a checked exception"));
    }

    /*
     * Provide a body for this method to make it throw the specified exception.
     * You must not use any deprecated methods.
     */
    public static void sneakyThrow(Throwable t) {

    }
}

class Missing {
    Missing() { }
}

public class Strange1 {
    public static void main(String[] args) {
        try {
            Missing m = new Missing();
        } catch (java.lang.NoClassDefFoundError ex) {
            System.out.println("Got it!");
        }
    }
}

public class Strange2 {
    public static void main(String[] args) {
        Missing m;
        try {
            m = new Missing();
        } catch (java.lang.NoClassDefFoundError ex) {
            System.out.println("Got it!");
        }
    } 
}

public class Workout {
    public static void main(String[] args) {
        workHard();
        System.out.println("It's nap time.");
    }

    private static void workHard() {
        try {
            workHard();
        } finally {
            workHard();
        }
    }
}