讀取檔案大小：1.45G
第一種，OldIO:
Java程式碼

1. publicstaticvoid oldIOReadFile() throws IOException{
2. BufferedReader br = new BufferedReader(new FileReader("G://lily_947.txt"));
3. PrintWriter pw = new PrintWriter("G://oldIO.tmp");
4. char[] c = newchar[100*1024*1024];
5. for(;;){
6. if(br.read(c)!=-1){
7. pw.print(c);
8. }else{
9. break;
10. }
11. }
12. pw.close();
13. br.close();
14. }

	public static void oldIOReadFile() throws IOException{
		BufferedReader br = new BufferedReader(new FileReader("G://lily_947.txt"));
		PrintWriter pw = new PrintWriter("G://oldIO.tmp");
		char[] c = new char[100*1024*1024];
		for(;;){
			if(br.read(c)!=-1){
				pw.print(c);
			}else{
				break;
			}
		}
		pw.close();
		br.close();
	}
 

耗時70.79s


第二種，newIO:
Java程式碼

1. publicstaticvoid newIOReadFile() throws IOException{
2. FileChannel read = new RandomAccessFile("G://lily_947.txt","r").getChannel();
3. FileChannel writer = new RandomAccessFile("G://newIO.tmp","rw").getChannel();
4. ByteBuffer bb = ByteBuffer.allocate(200*1024*1024);
5. while(read.read(bb)!=-
   1){
6. bb.flip();
7. writer.write(bb);
8. bb.clear();
9. }
10. read.close();
11. writer.close();
12. }

public static void newIOReadFile() throws IOException{
		FileChannel read = new RandomAccessFile("G://lily_947.txt","r").getChannel();
		FileChannel writer = new RandomAccessFile("G://newIO.tmp","rw").getChannel();
		ByteBuffer bb = ByteBuffer.allocate(200*1024*1024);
		while(read.read(bb)!=-1){
			bb.flip();
			writer.write(bb);
			bb.clear();
		}
		read.close();
		writer.close();
		
	}

耗時47.24s


第三種，RandomAccessFile:
Java程式碼

1. publicstaticvoid randomReadFile() throws IOException{
2. RandomAccessFile read = new RandomAccessFile("G://lily_947.txt","r");
3. RandomAccessFile writer = new RandomAccessFile("G://random.tmp","rw");
4. byte[] b = newbyte[200*1024*1024];
5. while(read.read(b)!=-1){
6. writer.write(b);
7. }
8. writer.close();
9. read.close();
10. }

public static void randomReadFile() throws IOException{
		RandomAccessFile read = new RandomAccessFile("G://lily_947.txt","r");
		RandomAccessFile writer = new RandomAccessFile("G://random.tmp","rw");
		byte[] b = new byte[200*1024*1024];
		while(read.read(b)!=-1){
			writer.write(b);
		}
		writer.close();
		read.close();
	}

耗時46.65

第四種，MappedByteBuffer：
Java程式碼

1. publicstaticvoid mappedBuffer() throws IOException{
2. FileChannel read = new FileInputStream("G://lily_947.txt").getChannel();
3. FileChannel writer = new RandomAccessFile("G://buffer.tmp","rw").getChannel();
4. long i = 0;
5. long size = read.size()/30;
6. ByteBuffer bb,cc = null;
7. while(i<read.size()&&(read.size()-i)>size){
8. bb = read.map(FileChannel.MapMode.READ_ONLY, i, size);
9. cc = writer.map(FileChannel.MapMode.READ_WRITE, i, size);
10. cc.put(bb);
11. i+=size;
12. bb.clear();
13. cc.clear();
14. }
15. bb = read.map(FileChannel.MapMode.READ_ONLY, i, read.size()-i);
16. cc.put(bb);
17. bb.clear();
18. cc.clear();
19. read.close();
20. writer.close();
21. }

public static void mappedBuffer() throws IOException{
		FileChannel read = new FileInputStream("G://lily_947.txt").getChannel();
		FileChannel writer = new RandomAccessFile("G://buffer.tmp","rw").getChannel();
		long i = 0;
		long size = read.size()/30;
		ByteBuffer bb,cc = null;
		while(i<read.size()&&(read.size()-i)>size){
			bb = read.map(FileChannel.MapMode.READ_ONLY, i, size);
			cc = writer.map(FileChannel.MapMode.READ_WRITE, i, size);
			cc.put(bb);
			i+=size;
			bb.clear();
			cc.clear();
		}
		bb = read.map(FileChannel.MapMode.READ_ONLY, i, read.size()-i);
		cc.put(bb);
		bb.clear();
		cc.clear();
		read.close();
		writer.close();
		
	}

耗時：36

前三種讀法對應的資源佔用圖如下：
相對於最後一種記憶體直接對映方式前面的測試其實無意義，基本秒殺。。。。。
對於很大的檔案直接分塊對映時記憶體會不夠，這是因為MappedByteBuffer未被釋放造成的，sun未提供直接回收MappedByteBuffer區域的方法，這個時候有兩種方法解決，第一種比較愚笨的：
Java程式碼

1. System.gc();
2. System.runFinalization();
3. try {
4. Thread.sleep(3000);
5. } catch (InterruptedException e) {
6. e.printStackTrace();
7. }

             System.gc(); 
            System.runFinalization(); 
            try {
				Thread.sleep(3000);
			} catch (InterruptedException e) {
				
				e.printStackTrace();
			}

第二種網上找來的，利用反射呼叫clean方法：
Java程式碼

1. publicstaticvoid unmap(final MappedByteBuffer buffer) {
2. if (buffer == null) {
3. return;
4. }
5. AccessController.doPrivileged(new PrivilegedAction<Object>() {
6. public Object run() {
7. try {
8. Method getCleanerMethod = buffer.getClass().getMethod("cleaner", new Class[0]);
9. if (getCleanerMethod != null) {
10. getCleanerMethod.setAccessible(true);
11. Object cleaner = getCleanerMethod.invoke(buffer, new Object[0]);
12. Method cleanMethod = cleaner.getClass().getMethod("clean", new Class[0]);
13. if (cleanMethod != null) {
14. cleanMethod.invoke(cleaner, new Object[0]);
15. }
16. }
17. } catch (Exception e) {
18. e.printStackTrace();
19. }
20. returnnull;
21. }
22. });
23. }

public static void unmap(final MappedByteBuffer buffer) {
		if (buffer == null) {
			return;
		}
		AccessController.doPrivileged(new PrivilegedAction<Object>() {
			public Object run() {
				try {
					Method getCleanerMethod = buffer.getClass().getMethod("cleaner", new Class[0]);
					if (getCleanerMethod != null) {
						getCleanerMethod.setAccessible(true);
						Object cleaner = getCleanerMethod.invoke(buffer, new Object[0]);
						Method cleanMethod = cleaner.getClass().getMethod("clean", new Class[0]);
						if (cleanMethod != null) {
							cleanMethod.invoke(cleaner, new Object[0]);
						}
					}
				} catch (Exception e) {
					e.printStackTrace();
				}
				return null;
			}
 
		});
	}

以上兩種方法感覺都彆扭，還有就是可以自己分割成物理檔案再迴圈呼叫，這個也不太美觀。
速度也會減慢好多。