ex8(5).java

JAVA编程思想第四版英文原版习题答案. pdf原版的

// containers/Ex8.java
// TIJ4 Chapter Containers, Exercise 8, page 821
/* Create a generic, singly linked list class called SList, which, to keep
* things simple, does not implement the List interface. Each Link object in
* the list should contain a reference to the next element in the list, but
* not the previous one (LinkedList, in contrast, is a doubly linked list, 
* which means it maintains links in both directions). Create your own 
* SListIterator which, again for simplicity, does not implement ListIterator.
* The only method in SList other than toString() should be iterator(), which
* produces an SListIterator. The only way to insert and remove elements from 
* an SList is through SListIterator. Write code to demonstrate SList. 
*/
import java.util.*;
import static org.greggordon.tools.Print.*;

class SList<E> {
	private Link<E> headLink = new Link<E>(null);
	SListIterator<E> iterator() { return new SListIterator<E>(headLink); }
	public String toString() { 
		if(headLink.next == null) return "SList: []";
		print("SList: [");
		SListIterator<E> it = this.iterator();
		StringBuilder s = new StringBuilder(); 
		while(it.hasNext()) {
			s.append(it.next() + (it.hasNext() ? ", " : ""));
		}
		return s + "]";
	}		
}

class SListIterator<E> {
	Link<E> current;
	SListIterator(Link<E> link) {
		current = link;
	}
	public boolean hasNext() {
		return current.next != null;
	}
	public Link<E> next() {
		current = current.next;
		return current;
	}
	public void insert(E e) {
		current.next = new Link<E>(e, current.next);
		current = current.next;
	}	
	public void remove() {
		if(current.next != null) {
			current.next = current.next.next;
		}
	}
}

class Link<E> {
	E e;
	Link<E> next;
	Link(E e, Link<E> next) { 
		this.e = e;
		this.next = next; 
	}
	Link(E e) {
		this(e, null);
	} 	
	public String toString() {
		if(e == null) return "null";
		return e.toString();
	}
}

public class Ex8 {
	public static void main(String[] args) {
		SList<String> sl = new SList<String>();
		println(sl);
		SListIterator<String> slIter = sl.iterator();
		println("inserting \"hi\"");
		slIter.insert("hi");
		println(sl);
		println("inserting \"there\"");
		slIter.insert("there");
		println(sl);
		println("inserting \"sweetie\"");
		slIter.insert("sweetie");
		println(sl);
		println("inserting \"pie\"");
		slIter.insert("pie");
		println(sl);
		SListIterator<String> slIter2 = sl.iterator();
		println("removing \"hi\"");
		slIter2.remove();
		println(sl);
		println("inserting \"hello\"");
		slIter2.insert("hello");
		println(sl);
		println("removing \"there\"");
		slIter2.remove();
		println(sl);
		println("removing \"sweetie\"");
		slIter2.remove();
		println(sl);
		println("removing \"pie\"");
		slIter2.remove();
		println(sl);
		println("removing \"hello\"");
		SListIterator slIter3 = sl.iterator();
		slIter3.remove();
		println(sl);		
	}
}