在2009年的JavaOne大会上，Joshua Bloch和Neal Gafter又为我们带来的7道谜题，挺有意思的。大家不妨看看。
摘自：
Return of the Puzzlers: Schlock and Awe
Joshua Bloch, Google, Inc.; Neal Gafter, Microsoft
http://developers.sun.com/learning/javaoneonline/sessions/2009/pdf/TS-5186.pdf
1.Life's Persistent Questions
- Java code
public class SimpleQuestion { static boolean yesOrNo(String s) { s = s.toLowerCase(); if (s.equals("yes") || s.equals("y") || s.equals("t")) { s = "true"; } return Boolean.getBoolean(s); } public static void main(String[] args) { System.out.println(yesOrNo("true") + " " + yesOrNo("Yes")); }}问题：程序打印什么？
如果熟悉Boolean.getBoolean（）这个方法的话，应该不会出错。方法的功能参考文档。
2.Instruments of Tortue
- Java code
import java.util.Arrays;import java.util.Collection;import java.util.HashSet;public class InstrumentedHashSet<E> extends HashSet<E> { private int addCount = 0; @Override public boolean add(E e){ addCount++; return super.add(e); } @Override public boolean addAll(Collection<? extends E> c){ addCount += c.size(); return super.addAll(c); } public static void main(String[] args) { InstrumentedHashSet<String> s = new InstrumentedHashSet<String>(); s.addAll(Arrays.asList("Accordion","Banjo","Kazoo")); System.out.println(s.addCount); }}问题：打印结果是什么？
这个看第一遍可能会出错，不过也算容易理解。
3.Iterator Titillator
- Java code
import java.util.Iterator;import java.util.NoSuchElementException;public abstract class AbstractIterator<T> implements Iterator<T> { T next = nextElement(); public boolean hasNext() { return next != null; } public T next() { if (next == null) { throw new NoSuchElementException(); } T result = next; next = nextElement(); return result; } public void remove() { throw new UnsupportedOperationException(); } protected abstract T nextElement(); private static Iterator<Character> test(final String s) { return new AbstractIterator<Character>() { private int cursor = 0; protected Character nextElement() { return cursor == s.length() ? null : s.charAt(cursor++); } }; } public static void main(String[] args) { for (Iterator<Character> i = test("OPS"); i.hasNext();) { System.out.print(i.next()); } }}
问题：输出结果是什么？
理解如何正确的设计Iterator。
4.Search for the One
- Java code
import java.util.ArrayList;import java.util.Collections;import java.util.Comparator;import java.util.List;public class Searching { public static void main(String[] args) { String[] strings = { "0", "1", "2", "3", "4", "5"}; List<Integer> integers = new ArrayList<Integer>(); for(String s : strings){ integers.add(Integer.valueOf(s)); } System.out.println(Collections.binarySearch(integers, 1,cmp)); } static Comparator<Integer> cmp = new Comparator<Integer>(){ public int compare(Integer i,Integer j){ return i<j?-1:(i==j?0:1); } };}