学习笔记：Java基础查缺补漏（三）

来源于慕课网Java零基础入门

好多基础的东西都忘记了，补起来！

• 线程
• 流

线程

创建线程的几类方法

• 继承Thread类

public static void func1() {
        class MyThread extends Thread {
            MyThread(String id) {
                super(id);
            }
            @Override
            public void run() {
                int i = 0;
                while ( i < 20 ) {
                    System.out.println("t" + this.getName() + " " + i++);
                }
            }
        }

        new MyThread("1").start();
        new MyThread("2").start();
    }

• 实现Runnable接口

public static void func2() {
        class MyThread implements Runnable {

            @Override
            public void run() {
                int i = 0;
                while ( i < 20 ) {
                    System.out.println("t" + Thread.currentThread().getName() + " " + i++);
                }
            }
        }

        new Thread(new MyThread()).start();
        new Thread(new MyThread()).start();
    }

• 实现Callable接口

public static void func3() {
        FutureTask<String> futureTask = new FutureTask<>(new Callable<String>() {
            @Override
            public String call() throws Exception {
                Thread.sleep(1000);
                return "第三种创建方式";
            }
        });

        new Thread(futureTask).start();

        try {
            String output = futureTask.get();
            System.out.println(output);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

Sleep方法使用

注意，因为线程调度的一些因素，从停止到开始的时间间隔可能会大于设定的时长

public static void func4(){
        new Thread(new Runnable() {
            @Override
            public void run() {
                int i = 0;
                while ( i < 50 ) {
                    System.out.println("t" + Thread.currentThread().getName() + " " + i++);
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();
    }

其他

• 调用join()/join(millionsecond)的线程优先执行

  • 可以在主线程中调用子线程的这个方法来使其等到子线程运行结束

• 调用方法 getPriority, setPriority 对其优先级进行操作，优先级从小到大1-10，默认为5

• 线程间通信

  • wait() 阻塞
  • notify() 唤醒
  • notifyAll()

---

流

字节流 对二进制进行操作

• InputStream 输入

• OutputStream 输出

• FileInputStream
  • public int read() 读一个字节
  • public inr read(byte[] b) 读入一个字节数组中 -1表示已经读到了末尾
  • public int read(byte[] b, int off, int len)
  • public void close() 关闭

int n;
while ((n = fis.read()) != -1) {...}
fis.close();

• FileOutputStream

  • FileOutputStream(File, ”是否追加“)
  • public void write(int b) 写一个字节
  • public void write(byte[] b) 写一个字节数组
  • public void write(byte[] b, int off, int length)
  • public void close()

• 对文件的拷贝

byte[] b = new byte[1024];
while((n = fis.read(b))!=1){
  fos.write(b, 0, n);
}

• BufferedInputStream

• BufferedOutputStream

/**
 * 项目名：learning
 * 包名：  com.example.io
 * 描述：  三种方法实现对文件的拷贝
 *
 * @author schwarzeni
 * @date 2018/12/29 8:29 AM
 */
public class Copy {

    private static File srcFile = new File("image1.png");
    private static File destFile = new File("image1-copy.png");
    private static int bufferSize = 1024;

    private static void copy1() throws FileNotFoundException, IOException {
        InputStream inputStream = new FileInputStream(srcFile);
        OutputStream outputStream = new FileOutputStream(destFile);

        byte[] buffer = new byte[bufferSize];
        int len;
        while ((len = inputStream.read(buffer)) != -1) {
            outputStream.write(buffer, 0, len);
        }

        inputStream.close();
        outputStream.close();
    }

    public static void copy2() throws IOException {
        InputStream inputStream = new FileInputStream(srcFile);
        OutputStream outputStream = new FileOutputStream(destFile);

        BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream);
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream);

        byte[] buffer = new byte[bufferSize];
        int len;
        while ((len = inputStream.read(buffer)) != -1) {
            outputStream.write(buffer, 0, len);
        }

        bufferedInputStream.close();
        bufferedOutputStream.flush();
        bufferedOutputStream.close();
        inputStream.close();
        outputStream.close();
    }

    public static void copy3() {
      FileChannel srcFileChannel;
      FileChannel destFileChannel;
        try {
            RandomAccessFile srcFile = new RandomAccessFile(this.srcFilePath, "rw");
            RandomAccessFile destFile = new RandomAccessFile(this.destFilePath, "rw");
            srcFile.seek(idx);
            destFile.seek(idx);
            srcFileChannel = srcFile.getChannel();
            destFileChannel = destFile.getChannel();
            ByteBuffer byteBuffer = ByteBuffer.allocate(this.bufferSize);
            byteBuffer.flip();

            srcFileChannel.transferTo(this.idx, this.length, destFileChannel);
            srcFileChannel.close();
            destFileChannel.close();
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }
}

字符流

• Reader

• Writer

• InputStreamReader(FileInputStream, “utf-8”)

• OutputStreamWriter(FileOutputStrea, “GBK”)

  • getEncodings

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对象序列化

• Serializable 接口
• ObjectInputStream(Inputstream)
• ObjectOutputStream()