面试刷题11:java系统中io的分类有哪些？

随着分布式技术的普及和海量数据的增长，io的能力越来越重要，java提供的io模块提供了足够的扩展性来适应。

我是李福春，我在准备面试，今天的问题是：

java中的io有哪几种？

java中的io分3类：

1，bio ,即同步阻塞io,对应java.io包提供的工具；基于流模型，虽然直观，代码实现也简单，但是扩展性差，消耗资源大，容易成为系统的瓶颈；


2，nio，同步非阻塞io,对应java.nio包提供的工具，基于io多路复用；
核心类： channel ,selector , buffer , charset  
selector是io多路复用的基础，实现了一个线程高效管理多个客户端连接，通过事件监听处理感兴趣的事件。

3，aio,即异步非阻塞io, 基于事件和回调

io的类层级

java各种io的例子

java.io客户端连接服务端例子

package org.example.mianshi.io;

import java.io.bufferedreader;
import java.io.ioexception;
import java.io.inputstreamreader;
import java.io.printwriter;
import java.net.inetaddress;
import java.net.serversocket;
import java.net.socket;

/**
 * 说明：传统流式io 客户端连接服务端例子
 * @author carter
 * 创建时间： 2020年03月25日 9:58 下午
 **/

public class javaioapp {

    public static void main(string[] args) {

        final server server = new server();
        new thread(server).start();

        try (
                socket socket = new socket(inetaddress.getlocalhost(), server.getport());
        ) {
            final bufferedreader bufferedreader = new bufferedreader(new inputstreamreader(socket.getinputstream()));

            bufferedreader.lines().foreach(system.out::println);

        } catch (ioexception e) {
            e.printstacktrace();
        }
    }

    public static class server implements runnable {

        private serversocket serversocket;

        public int getport() {
            return serversocket.getlocalport();
        }

        @override
        public void run() {

            try (serversocket serversocket = new serversocket(0);) {

                this.serversocket = serversocket;
                while (true) {
                    final socket socket = serversocket.accept();
                    new requesthandler(socket).start();
                }

            } catch (ioexception e) {
                e.printstacktrace();
            }

        }

        private class requesthandler extends thread {
            private socket socket;

            public requesthandler(socket socket) {
                this.socket = socket;
            }

            @override
            public void run() {
                try (
                        final printwriter printwriter = new printwriter(socket.getoutputstream());
                ) {

                    printwriter.write("hello world");
                    printwriter.flush();

                } catch (ioexception e) {
                    e.printstacktrace();
                }
            }
        }
    }
}

使用连接池优化

package org.example.mianshi.io;

import java.io.bufferedreader;
import java.io.ioexception;
import java.io.inputstreamreader;
import java.io.printwriter;
import java.net.inetaddress;
import java.net.serversocket;
import java.net.socket;
import java.util.concurrent.executorservice;
import java.util.concurrent.executors;

/**
 * 说明：传统流式io 客户端连接服务端例子
 * @author carter
 * 创建时间： 2020年03月25日 9:58 下午
 **/

public class threadpooljavaioapp {

    public static void main(string[] args) {

        final server server = new server();
        new thread(server).start();

        try (
                socket socket = new socket(inetaddress.getlocalhost(), server.getport());
        ) {
            final bufferedreader bufferedreader = new bufferedreader(new inputstreamreader(socket.getinputstream()));

            bufferedreader.lines().foreach(system.out::println);

        } catch (ioexception e) {
            e.printstacktrace();
        }
    }

    public static class server implements runnable {

        private executorservice threadpool = executors.newfixedthreadpool(4);

        private serversocket serversocket;

        public int getport() {
            return serversocket.getlocalport();
        }

        @override
        public void run() {

            try (serversocket serversocket = new serversocket(0);) {

                this.serversocket = serversocket;
                while (true) {
                    final socket socket = serversocket.accept();

                    threadpool.submit(new requesthandler(socket));
                }

            } catch (ioexception e) {
                e.printstacktrace();
            }finally {
                threadpool.shutdown();
            }

        }

        private class requesthandler implements runnable {
            private socket socket;

            public requesthandler(socket socket) {
                this.socket = socket;
            }

            @override
            public void run() {
                try (
                        final printwriter printwriter = new printwriter(socket.getoutputstream());
                ) {

                    printwriter.write("hello world");
                    printwriter.flush();

                } catch (ioexception e) {
                    e.printstacktrace();
                }
            }
        }
    }
}

java.nio例子

package org.example.mianshi.io;

import java.io.bufferedreader;
import java.io.ioexception;
import java.io.inputstreamreader;
import java.net.inetaddress;
import java.net.inetsocketaddress;
import java.net.socket;
import java.nio.channels.selectionkey;
import java.nio.channels.selector;
import java.nio.channels.serversocketchannel;
import java.nio.channels.socketchannel;
import java.nio.charset.charset;

/**
 * 说明：nio的客户端连接服务端例子
 * @author carter
 * 创建时间： 2020年03月25日 10:32 下午
 **/

public class javanioapp {

    public static void main(string[] args) {

        new server().start();

        try (
                socket socket = new socket(inetaddress.getlocalhost(), 8888);
        ) {
            final bufferedreader bufferedreader = new bufferedreader(new inputstreamreader(socket.getinputstream()));

            bufferedreader.lines().foreach(system.out::println);

        } catch (ioexception e) {
            e.printstacktrace();
        }
    }

    public static class server extends thread {

        @override
        public void run() {

            try {
                serversocketchannel serversocketchannel = serversocketchannel.open();

                serversocketchannel.bind(new inetsocketaddress(inetaddress.getlocalhost(), 8888));

                serversocketchannel.configureblocking(false);

                final selector selector = selector.open();

                serversocketchannel.register(selector, selectionkey.op_accept);

                while (true) {

                    selector.select();
                    selector.selectedkeys().foreach(selectionkey -> {
                        sayhelloworld((serversocketchannel) selectionkey.channel());
                    });

                }

            } catch (ioexception e) {
                e.printstacktrace();
            }

        }

        private void sayhelloworld(serversocketchannel channel) {

            try (socketchannel socketchannel = channel.accept()) {

                socketchannel.write(charset.defaultcharset().encode("hello world nio"));

            } catch (ioexception e) {
                e.printstacktrace();
            }

        }
    }

}


java.nio2例子

package org.example.mianshi.io;

import java.io.bufferedreader;
import java.io.ioexception;
import java.io.inputstreamreader;
import java.net.inetaddress;
import java.net.inetsocketaddress;
import java.net.socket;
import java.nio.channels.asynchronousserversocketchannel;
import java.nio.channels.asynchronoussocketchannel;
import java.nio.channels.completionhandler;
import java.nio.charset.charset;

/**
 * 说明：todo
 * @author carter
 * 创建时间： 2020年03月25日 10:54 下午
 **/

public class javanio2app {

    public static void main(string[] args) {

        new server().start();

        try (
                socket socket = new socket(inetaddress.getlocalhost(), 9999);
        ) {
            final bufferedreader bufferedreader = new bufferedreader(new inputstreamreader(socket.getinputstream()));

            bufferedreader.lines().foreach(system.out::println);

        } catch (ioexception e) {
            e.printstacktrace();
        }


    }

    public static class server extends thread {


        @override
        public void run() {

            try {
                asynchronousserversocketchannel serversocketchannel = asynchronousserversocketchannel.open()
                        .bind(new inetsocketaddress(inetaddress.getlocalhost(), 9999));

                serversocketchannel.accept(serversocketchannel, new completionhandler<asynchronoussocketchannel, asynchronousserversocketchannel>() {
                    @override
                    public void completed(asynchronoussocketchannel socketchannel,
                                          asynchronousserversocketchannel serversocketchannel1) {
//                        serversocketchannel1.accept(socketchannel, this);

                        socketchannel.write(charset.defaultcharset().encode("hello world nio2 "));

                        try {
                            socketchannel.close();
                        } catch (ioexception e) {
                            e.printstacktrace();
                        }
                    }

                    @override
                    public void failed(throwable exc, asynchronousserversocketchannel attachment) {
                        exc.printstacktrace();
                    }
                });

            } catch (ioexception e) {
                e.printstacktrace();
            }


        }
    }

}

本例子暂时无法运行。只为展示过程；

小结

本篇主要介绍了java提供的3中io，即 bio,nio,aio ; 并提供了一些示例代码辅助理解。

原创不易，转载请注明出处。