finish JVM first week homework: ClassFileLoader.java and LRUpageFrame.java

group24/1525619747/homework_20170402/src/com/coderising/jvm/loader/ClassFileLoader.java

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+package com.coderising.jvm.loader;
+
+import java.io.BufferedInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.DataInputStream;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+
+
+public class ClassFileLoader {
+
+	private List<String> clzPaths = new ArrayList<String>();
+
+	public byte[] readBinaryCode(String className) throws IOException {
+		String clzFileName = "";
+		byte[] byteCodes = null;
+		boolean classFound = false;
+
+		for (String path : clzPaths) {
+			clzFileName = path + File.separatorChar + className.replace('.', File.separatorChar) + ".class";
+
+			if ((byteCodes = loadClassFile(clzFileName)) != null){
+				classFound = true;
+				return byteCodes;
+			}			   
+		}
+
+		if (classFound == false) {
+			throw new FileNotFoundException(clzFileName);
+		}
+
+		return null;		
+	}
+
+	private byte[] loadClassFile(String clzFileName) throws IOException {
+
+		File file = new File(clzFileName);  
+        if(!file.exists()){  
+//            throw new FileNotFoundException(clzFileName);
+        	return null;
+        }
+
+        ByteArrayOutputStream bos = new ByteArrayOutputStream((int)file.length());
+        BufferedInputStream in = null;
+
+        try {
+        	in = new BufferedInputStream(new FileInputStream(file));
+
+        	int buf_size = 1024;
+        	byte[] buffer = new byte[buf_size];
+        	int len = 0;
+
+        	while ((len = in.read(buffer, 0, buf_size)) != -1) {
+        		bos.write(buffer, 0, len);
+        	}
+
+        	return bos.toByteArray();
+
+        } catch (IOException e) {
+        	e.printStackTrace();
+        	throw e;
+        } finally {
+        	try {
+        		in.close();
+        	} catch (IOException e) {
+        		e.printStackTrace();
+        	}
+        	bos.close();
+        }
+	}
+
+
+
+	public void addClassPath(String path) {
+		clzPaths.add(path);
+	}
+
+	public String getClassPath_V1(){
+
+		return  null;
+	}
+
+	public String getClassPath(){
+		String classPath = "";
+		for (int i = 0; i < clzPaths.size(); i++) {
+			classPath += clzPaths.get(i);
+			if (i != clzPaths.size() - 1) {
+				classPath += ";";
+			}
+		}
+		return classPath;
+	}
+
+
+
+}

group24/1525619747/homework_20170402/src/com/coderising/jvm/test/ClassFileloaderTest.java

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+package com.coderising.jvm.test;
+
+import java.io.IOException;
+
+import org.junit.After;
+import  org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import com.coderising.jvm.loader.ClassFileLoader;
+
+
+public class ClassFileloaderTest {
+
+	static String path1 = "F:\\Project\\Java_Project\\Java_SE\\coding2017\\group24\\1525619747\\homework_20170402\\bin";
+	static String path2 = "C:\\temp";
+
+	@Before
+	public void setUp() throws Exception {		 
+	}
+
+	@After
+	public void tearDown() throws Exception {
+	}
+
+	@Test
+	public void testClassPath(){		
+
+		ClassFileLoader loader = new ClassFileLoader();
+		loader.addClassPath(path1);
+		loader.addClassPath(path2);
+
+		String clzPath = loader.getClassPath();
+		Assert.assertEquals(path1+";"+path2,clzPath);
+
+	}
+
+	@Test
+	public void testClassFileLength() throws IOException {		
+
+		ClassFileLoader loader = new ClassFileLoader();
+		loader.addClassPath(path1);
+
+		String className = "com.coderising.jvm.test.EmployeeV1";
+
+		byte[] byteCodes = loader.readBinaryCode(className);
+//		System.out.println(byteCodes.length);
+		// 注意：这个字节数可能和你的JVM版本有关系， 你可以看看编译好的类到底有多大
+		Assert.assertEquals(1056, byteCodes.length);
+
+	}
+
+
+    @Test	
+	public void testMagicNumber() throws IOException{
+    	ClassFileLoader loader = new ClassFileLoader();
+		loader.addClassPath(path1);
+		String className = "com.coderising.jvm.test.EmployeeV1";
+		byte[] byteCodes = loader.readBinaryCode(className);
+		System.out.println(byteCodes[0] + " " + byteCodes[1] + " " + byteCodes[2] + " " +byteCodes[3]);
+		byte[] codes = new byte[]{byteCodes[0],byteCodes[1],byteCodes[2],byteCodes[3]};
+
+
+		String acctualValue = this.byteToHexString(codes);
+//		System.out.println(acctualValue);
+		Assert.assertEquals("cafebabe", acctualValue);
+	}
+
+
+
+
+	private String byteToHexString(byte[] codes ){
+		StringBuffer buffer = new StringBuffer();
+		for(int i=0;i<codes.length;i++){
+			byte b = codes[i];
+			int value = b & 0xFF;
+			String strHex = Integer.toHexString(value);
+			if(strHex.length()< 2){
+				strHex = "0" + strHex;
+			}		
+			buffer.append(strHex);
+		}
+		return buffer.toString();
+	}
+
+}

group24/1525619747/homework_20170402/src/com/coderising/jvm/test/EmployeeV1.java

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+package com.coderising.jvm.test;
+
+public class EmployeeV1 {
+
+
+	private String name;
+    private int age;
+
+    public EmployeeV1(String name, int age) {
+        this.name = name;
+        this.age = age;        
+    }    
+
+    public void setName(String name) {
+        this.name = name;
+    }
+    public void setAge(int age){
+    	this.age = age;
+    }
+    public void sayHello() {        
+    	System.out.println("Hello , this is class Employee ");    	
+    }
+    public static void main(String[] args){
+    	EmployeeV1 p = new EmployeeV1("Andy",29);
+    	p.sayHello();    
+
+    }
+
+}

group24/1525619747/homework_20170402/src/com/coderising/lru/LRUPageFrame.java

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+package com.coderising.lru;
+
+
+public class LRUPageFrame {
+
+	private static class Node {
+
+		Node prev;
+		Node next;
+		int pageNum;
+
+		Node() {
+			prev = null;
+			next = null;
+		}
+		Node(int pageNum) {
+			this.pageNum = pageNum;
+			prev = null;
+			next = null;
+		}
+	}
+
+	private int capacity;
+
+	private int currentSize;
+	private Node first;// 链表头
+	private Node last;// 链表尾
+
+
+	public LRUPageFrame(int capacity) {
+		this.currentSize = 0;
+		this.capacity = capacity;
+
+	}
+
+	/**
+	 * 获取缓存中对象
+	 * 
+	 * @param key
+	 * @return
+	 */
+	public void access(int pageNum) {
+		Node node = find(pageNum);
+//		System.out.println(node + " " + isFull());
+		if (node != null) { // 队列中含有节点，移到头部
+			moveExistedNodeToHead(node);
+		} else { // 队列中没有该节点，需添加
+			node = new Node(pageNum);
+			if (!isFull()) {
+				// 在头部添加节点
+				addNodeToHead(node);
+			} else {
+				// 删掉尾部节点，再在头部添加节点
+				deleteLastNode();
+				addNodeToHead(node);
+			}
+		}
+	}
+
+	private void deleteLastNode() {
+		// TODO Auto-generated method stub
+		if (currentSize == 0) {
+			return;
+		}
+		if (currentSize == 1) {
+			first = last = null;
+			--currentSize;
+			return;
+		}
+		Node toDelete = last;
+		Node lastPrev = last.prev;
+		lastPrev.next = last.next;
+		last.next.prev = lastPrev;
+		last = lastPrev;
+		toDelete = null;
+		--currentSize;
+	}
+
+	private void addNodeToHead(Node node) {
+		// TODO Auto-generated method stub
+		if (first == null) {
+			first = last = node;
+			++currentSize;
+			return;
+		}
+		if (currentSize == 1) {
+			node.prev = first;
+			node.next = first;
+			first.prev = node;
+			first.next = node;
+			first = node;
+			++currentSize;
+			return;
+		}
+		node.prev = first.prev;
+		first.prev.next = node;
+		node.next = first;
+		first.prev = node;
+		first = node;
+		++currentSize;
+	}
+
+	private void moveExistedNodeToHead(Node node) {
+		// TODO Auto-generated method stub
+		if (node == first) {
+			return;
+		}
+		if (node == last) {
+			Node lastPrev = last.prev;
+			first = last;
+			last = lastPrev;
+			return;
+		}
+		node.prev.next = node.next;
+		node.next.prev = node.prev;
+
+		node.next = first;
+		node.prev = first.prev;
+		first.prev.next = node;
+		first.prev = node;
+		first = node;
+	}
+
+	private Node find(int pageNum) {
+		Node pointer = first;
+		while (pointer != null && pointer != last) {
+			if (pointer.pageNum == pageNum) {
+				return pointer;
+			}
+			pointer = pointer.next;
+		}
+		// pointer == last now
+		if (pointer != null && pointer.pageNum == pageNum) {
+			return pointer;
+		}
+
+		return null;
+	}
+
+	private boolean isFull() {
+		return (currentSize == capacity);
+	}
+
+	public String toString() {
+		StringBuilder buffer = new StringBuilder();
+		Node node = first;
+		// 由于个人实现的双链表是环链的，所以这里做了更改
+		while(node != null && node != last){
+			buffer.append(node.pageNum);			
+
+			node = node.next;
+			if(node != null){
+				buffer.append(",");
+			}
+		}
+		if (node != null) {
+			buffer.append(node.pageNum);
+		}
+		System.out.println(buffer.toString());
+		return buffer.toString();
+	}
+
+}