java IO速度比较

最新推荐文章于 2022-03-20 19:34:13 发布

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最新推荐文章于 2022-03-20 19:34:13 发布

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文章标签： java IO

本文链接：https://blog.youkuaiyun.com/u014434044/article/details/79882127

本文对比了Java中传统IO流、缓冲流和NIO在写文件速度上的表现。测试结果显示，传统IO流的写文件速度最慢，而缓冲流和NIO速度相近且快于传统IO，NIO在效率上稍占优势。NIO通过按块读写和利用操作系统优化IO操作，显著提升了性能。

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以写文件速度进行比较。分别比较传统IO流、缓冲流、和NIO的速度。均写80000k的数据。本次测试环境是jdk8

一、传统IO

	long l1 = System.currentTimeMillis();
	byte[] b = new byte[]{1,2,3,4,5,6,7,8};
	FileOutputStream fos = null;
	try {
		
		fos = new FileOutputStream("test.txt");
		for(int i=0;i<10240000;i++){
			fos.write(b);
		}
	} catch (FileNotFoundException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	} catch (IOException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	} finally {
		if(fos !=null){
			try {
				fos.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		long l2 = System.currentTimeMillis();
		System.out.println("FileOutputStream use time:" + (l2-l1));
	}

运行5次的结果：

FileOutputStream use time:37292

FileOutputStream use time:37588

FileOutputStream use time:36913

FileOutputStream use time:37772

二、缓冲流

		long l1 = System.currentTimeMillis();
		byte[] b = new byte[]{1,2,3,4,5,6,7,8};
		BufferedOutputStream bos = null;
		try {
			bos = new BufferedOutputStream(new FileOutputStream("test1.txt"), 10240);
			for(int i=0;i<10240000;i++){
				bos.write(b);
			}
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally{
			if(bos != null){
				try {
					bos.flush();
					bos.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			long l2 = System.currentTimeMillis();
			System.out.println("BufferedOutputStream use time:"+(l2-l1));
		}

运行5次结果：

BufferedOutputStream use time:345

BufferedOutputStream use time:342

BufferedOutputStream use time:490

BufferedOutputStream use time:344

BufferedOutputStream use time:341

三、NIO

	long l1 = System.currentTimeMillis();
	byte[] b = new byte[]{1,2,3,4,5,6,7,8};
	ByteBuffer bb = ByteBuffer.allocate(10240);
	FileOutputStream fos = null;
	FileChannel fc = null;
	try {
		fos = new FileOutputStream("test2.txt");
		fc = fos.getChannel();
		bb.clear();
		for(int i=0;i<8000;i++){
		bb.clear();
		int p = bb.position();
		int c = bb.capacity();
		while(p + b.length <= c){
			bb.put(b);
			p = bb.position();
		}
		bb.flip();
		fc.write(bb);
		}
	} catch (FileNotFoundException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	} catch (IOException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	} finally{
		try {
			if(fos != null){
				fos.close();
			}
			if(fc != null){
				fc.close();
			}
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		long l2 = System.currentTimeMillis();
		System.out.println("NIO use time:"+(l2-l1));
	}

运行5次结果：

NIO use time:207

NIO use time:215

NIO use time:204

NIO use time:212

NIO use time:200

从以上运行结果来看，传统的IO的写文件速度明显要低于缓冲流及NIO，缓冲流与NIO相差不大，NIO稍微快些。从jdk1.4以后出现了NIO，传统的IO流是按字节读写数据，NIO是按块读写数据，NIO将耗时最大的IO操作交给底层的操作系统来完成，这大大优化了IO速度。jdk1.4以后的java.io包的一些类的设计也是基于NIO的思想，提供按块读写数据。