Java练习案例，Java项目实战，集合框架

public class TreeMap{

public static abstract class AbstractCollection implements Set{}
public static abstract class AbstractSet extends AbstractCollection{}
public interface Iterator {
	boolean hasNext() ;
	E next() ;
}
public interface Set {
	Iterator iterator() ;
} 
public interface Map {
	
	interface Entry {
		K getKey() ;
		V getValue() ;
	}
	V get (Object key) ;
	boolean containsKey(Object key) ;
	
	default V getOrDefault(Object key , V defaultValue) {
		V v ;
		return (( v = get(key)) != null || containsKey(key)) ? v : defaultValue ;
	}
}
public static abstract class AbstractMap implements Map , Cloneable{
	public static class SimpleImmutableEntry