20170328_1702 3.26作业

group02/562768642/src/com/github/orajavac/coding2017/basic/linklist/LRUPageFrame.java

@@ -0,0 +1,133 @@
+package com.github.orajavac.coding2017.basic.linklist;
+
+public class LRUPageFrame {
+private static class Node {
+
+		Node prev;
+		Node next;
+		int pageNum=10000;
+		String flag;
+
+		Node() {
+		}
+	}
+
+	private int capacity;
+	private int length;
+
+
+	private Node first;// 链表头
+	private Node last;// 链表尾
+
+
+	public LRUPageFrame(int capacity) {
+
+		this.capacity = capacity;
+
+		first = new Node();
+		last = new Node();
+		last.flag = "last";		//用来标识最后一个节点是链表尾，在这里链表尾并不算做内存页
+		first.flag = "first";	//用来标识链表头，在这里链表头并不算做内存页
+		first.next = last;
+		last.prev=first;
+	}
+
+	/**
+	 * 获取缓存中对象
+	 * 
+	 * @param key
+	 * @return
+	 */
+	public void access(int pageNum) {
+		if(lookup(pageNum)){
+			;
+		}else{
+			if (length<capacity){
+				addFirst(pageNum);
+			}else{
+				remove(pageNum);	//删除尾元素
+				addFirst(pageNum);
+			}
+		}
+	}
+
+	public boolean lookup(int pageNum){
+		Node nodef = first;
+		Node nodel = last;
+
+		//判断要找的元素是否在第一个节点里
+		if (nodef.next.pageNum == pageNum){
+			return true;
+		}
+
+		//判断要找的元素是否在最后一个节点里
+		if (nodel.prev.pageNum == pageNum){
+			remove(pageNum);	//删除尾元素
+			addFirst(pageNum);	//把访问pageNum添加到第一个节点里
+			return true;
+		}
+
+		while(nodef.next!=null&&nodef.next.pageNum != 999){
+			if (nodef.next.pageNum == pageNum){
+				nodef.next = nodef.next.next;	//先删除元素
+				nodef.next.prev = nodef;
+				addFirst(pageNum);	//再把访问添加元素
+				return true;
+			}
+			nodef = nodef.next;
+		}
+		return false;
+	}
+
+	public void remove(int pageNum){
+		length--;
+		Node n = last.prev;
+		last.prev = n.prev;
+		n.prev.next = last;
+	}
+
+	public void addFirst(int pageNum){
+		Node s = first.next;
+		Node n = new Node();
+		n.pageNum=pageNum;
+		n.next=s;
+		s.prev=n;
+		first.next=n;
+		length++;
+	}
+
+	public String toString(){
+		StringBuilder buffer = new StringBuilder();
+		Node node = first;
+		while(node.next.flag != "last"){
+			buffer.append(node.next.pageNum);			
+
+			node = node.next;
+
+			if(node.next.flag != "last"){
+				buffer.append(",");
+			}
+
+		}
+		return buffer.toString();
+	}
+
+	/**
+	 * 测试双向链表逆序输出
+	 * @return
+	 */
+	public String lastToString(){
+		StringBuilder buffer = new StringBuilder();
+		Node node = last;
+		while(node.prev!=null&&node.prev.flag != "first"){
+			buffer.append(node.prev.pageNum);			
+
+			node = node.prev;
+
+			if(node.prev!=null&&node.prev.flag != "first"){
+				buffer.append(",");
+			}
+		}
+		return buffer.toString();
+	}
+}

group02/562768642/src/com/github/orajavac/coding2017/basic/linklist/LRUPageFrameTest.java

@@ -0,0 +1,29 @@
+package com.github.orajavac.coding2017.basic.linklist;
+
+import org.junit.Test;
+
+import junit.framework.Assert;
+
+public class LRUPageFrameTest {
+
+	@Test
+	public void testAccess() {
+		LRUPageFrame frame = new LRUPageFrame(3);
+		frame.access(7);
+		frame.access(0);
+		frame.access(1);
+		Assert.assertEquals("1,0,7", frame.toString());
+		frame.access(2);
+		Assert.assertEquals("2,1,0", frame.toString());
+		frame.access(0);
+		Assert.assertEquals("0,2,1", frame.toString());
+		frame.access(0);
+		Assert.assertEquals("0,2,1", frame.toString());
+		frame.access(3);
+		Assert.assertEquals("3,0,2", frame.toString());
+		frame.access(0);
+		Assert.assertEquals("0,3,2", frame.toString());
+		frame.access(4);
+		Assert.assertEquals("4,0,3", frame.toString());
+	}
+}