java-IO流-其他流

###22.01_IO流(序列流)(了解)
* 1.什么是序列流
    * 序列流可以把多个字节输入流整合成一个, 从序列流中读取数据时, 将从被整合的第一个流开始读, 读完一个之后继续读第二个, 以此类推.
* 2.使用方式
    * 整合两个: SequenceInputStream(InputStream, InputStream)
    * 
            FileInputStream fis1 = new FileInputStream("a.txt");            //创建输入流对象,关联a.txt
            FileInputStream fis2 = new FileInputStream("b.txt");            //创建输入流对象,关联b.txt
            SequenceInputStream sis = new SequenceInputStream(fis1, fis2);    //将两个流整合成一个流
            FileOutputStream fos = new FileOutputStream("c.txt");            //创建输出流对象,关联c.txt
            
            int b;
            while((b = sis.read()) != -1) {                                    //用整合后的读
                fos.write(b);                                                //写到指定文件上
            }
            
            sis.close();
            fos.close();

###22.02_IO流(序列流整合多个)(了解)
* 整合多个: SequenceInputStream(Enumeration)
* 
        FileInputStream fis1 = new FileInputStream("a.txt");    //创建输入流对象,关联a.txt
        FileInputStream fis2 = new FileInputStream("b.txt");    //创建输入流对象,关联b.txt
        FileInputStream fis3 = new FileInputStream("c.txt");    //创建输入流对象,关联c.txt
        Vector<InputStream> v = new Vector<>();                    //创建vector集合对象
        v.add(fis1);                                            //将流对象添加
        v.add(fis2);
        v.add(fis3);
        Enumeration<InputStream> en = v.elements();                //获取枚举引用
        SequenceInputStream sis = new SequenceInputStream(en);    //传递给SequenceInputStream构造
        FileOutputStream fos = new FileOutputStream("d.txt");
        int b;
        while((b = sis.read()) != -1) {
            fos.write(b);
        }
    
        sis.close();
        fos.close();

###22.03_IO流(内存输出流*****)(掌握)
* 1.什么是内存输出流
    * 该输出流可以向内存中写数据, 把内存当作一个缓冲区, 写出之后可以一次性获取出所有数据
* 2.使用方式
    * 创建对象: new ByteArrayOutputStream()
    * 写出数据: write(int), write(byte[])
    * 获取数据: toByteArray()
    * 
            FileInputStream fis = new FileInputStream("a.txt");
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            int b;
            while((b = fis.read()) != -1) {
                baos.write(b);
            }
            
            //byte[] newArr = baos.toByteArray();                //将内存缓冲区中所有的字节存储在newArr中
            //System.out.println(new String(newArr));
            System.out.println(baos);
            fis.close();

###22.04_IO流(内存输出流之黑马面试题)(掌握)
* 定义一个文件输入流,调用read(byte[] b)方法,将a.txt文件中的内容打印出来(byte数组大小限制为5)
* 
            FileInputStream fis = new FileInputStream("a.txt");                //创建字节输入流,关联a.txt
            ByteArrayOutputStream baos = new ByteArrayOutputStream();        //创建内存输出流
            byte[] arr = new byte[5];                                        //创建字节数组,大小为5
            int len;
            while((len = fis.read(arr)) != -1) {                            //将文件上的数据读到字节数组中
                baos.write(arr, 0, len);                                    //将字节数组的数据写到内存缓冲区中
            }
            System.out.println(baos);                                        //将内存缓冲区的内容转换为字符串打印
            fis.close();

###22.05_IO流(随机访问流概述和读写数据)(了解)
* A:随机访问流概述
    * RandomAccessFile概述
    * RandomAccessFile类不属于流，是Object类的子类。但它融合了InputStream和OutputStream的功能。
    * 支持对随机访问文件的读取和写入。

* B:read(),write(),seek()
    
###22.06_IO流(对象操作流ObjecOutputStream)(了解)
* 1.什么是对象操作流
    * 该流可以将一个对象写出, 或者读取一个对象到程序中. 也就是执行了序列化和反序列化的操作.
* 2.使用方式
    * 写出: new ObjectOutputStream(OutputStream), writeObject()

public class Demo3_ObjectOutputStream {
    
                /**
                 * @param args
                 * @throws IOException 
                 * 将对象写出,序列化
                 */
                public static void main(String[] args) throws IOException {
                    Person p1 = new Person("张三", 23);
                    Person p2 = new Person("李四", 24);
            //        FileOutputStream fos = new FileOutputStream("e.txt");
            //        fos.write(p1);
            //        FileWriter fw = new FileWriter("e.txt");
            //        fw.write(p1);
                    //无论是字节输出流,还是字符输出流都不能直接写出对象
                    ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("e.txt"));//创建对象输出流
                    oos.writeObject(p1);
                    oos.writeObject(p2);
                    oos.close();
                }
            
            }

###22.07_IO流(对象操作流ObjectInputStream)(了解)
* 读取: new ObjectInputStream(InputStream), readObject()
    * 
            public class Demo3_ObjectInputStream {

/**
                 * @param args
                 * @throws IOException 
                 * @throws ClassNotFoundException 
                 * @throws FileNotFoundException 
                 * 读取对象,反序列化
                 */
                public static void main(String[] args) throws IOException, ClassNotFoundException {
                    ObjectInputStream ois = new ObjectInputStream(new FileInputStream("e.txt"));
                    Person p1 = (Person) ois.readObject();
                    Person p2 = (Person) ois.readObject();
                    System.out.println(p1);
                    System.out.println(p2);
                    ois.close();
                }
            
            }
    
###22.08_IO流(对象操作流优化)(了解)
*　将对象存储在集合中写出

Person p1 = new Person("张三", 23);
    Person p2 = new Person("李四", 24);
    Person p3 = new Person("马哥", 18);
    Person p4 = new Person("辉哥", 20);
    
    ArrayList<Person> list = new ArrayList<>();
    list.add(p1);
    list.add(p2);
    list.add(p3);
    list.add(p4);
    
    ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("f.txt"));
    oos.writeObject(list);                                    //写出集合对象
    
    oos.close();
* 读取到的是一个集合对象

ObjectInputStream ois = new ObjectInputStream(new FileInputStream("f.txt"));
            ArrayList<Person> list = (ArrayList<Person>)ois.readObject();    //泛型在运行期会被擦除,索引运行期相当于没有泛型
        //想去掉黄色可以加注解            
        @SuppressWarnings("unchecked")
            for (Person person : list) {
                System.out.println(person);
            }
        
        ois.close();

###22.09_IO流(加上id号)(了解)
* 注意
    * 要写出的对象必须实现Serializable接口才能被序列化
    * 不用必须加id号

###22.10_IO流(数据输入输出流)(了解)
* 1.什么是数据输入输出流
    * DataInputStream, DataOutputStream可以按照基本数据类型大小读写数据
    * 例如按Long大小写出一个数字, 写出时该数据占8字节. 读取的时候也可以按照Long类型读取, 一次读取8个字节.
* 2.使用方式
    * DataOutputStream(OutputStream), writeInt(), writeLong()

DataOutputStream dos = new DataOutputStream(new FileOutputStream("b.txt"));
            dos.writeInt(997);
            dos.writeInt(998);
            dos.writeInt(999);
            
            dos.close();
    * DataInputStream(InputStream), readInt(), readLong()

DataInputStream dis = new DataInputStream(new FileInputStream("b.txt"));
            int x = dis.readInt();
            int y = dis.readInt();
            int z = dis.readInt();
            System.out.println(x);
            System.out.println(y);
            System.out.println(z);
            dis.close();

###22.11_IO流(打印流的概述和特点)(掌握)
* 1.什么是打印流
    * 该流可以很方便的将对象的toString()结果输出, 并且自动加上换行, 而且可以使用自动刷出的模式
    * System.out就是一个PrintStream, 其默认向控制台输出信息

PrintStream ps = System.out;
            ps.println(97);                    //其实底层用的是Integer.toString(x),将x转换为数字字符串打印
            ps.println("xxx");
            ps.println(new Person("张三", 23));
            Person p = null;
            ps.println(p);                    //如果是null,就返回null,如果不是null,就调用对象的toString()
* 2.使用方式
    * 打印: print(), println()
    * 自动刷出: PrintWriter(OutputStream out, boolean autoFlush, String encoding) 
    * 打印流只操作数据目的

PrintWriter pw = new PrintWriter(new FileOutputStream("g.txt"), true);
            pw.write(97);
            pw.print("大家好");
            pw.println("你好");                //自动刷出,只针对的是println方法
            pw.close();

###22.12_IO流(标准输入输出流概述和输出语句)
* 1.什么是标准输入输出流(掌握)
    * System.in是InputStream, 标准输入流, 默认可以从键盘输入读取字节数据
    * System.out是PrintStream, 标准输出流, 默认可以向Console中输出字符和字节数据
* 2.修改标准输入输出流(了解)
    * 修改输入流: System.setIn(InputStream)
    * 修改输出流: System.setOut(PrintStream)
    * 
            System.setIn(new FileInputStream("a.txt"));                //修改标准输入流
            System.setOut(new PrintStream("b.txt"));                //修改标准输出流
            
            InputStream in = System.in;                                //获取标准输入流
            PrintStream ps = System.out;                            //获取标准输出流
            int b;
            while((b = in.read()) != -1) {                            //从a.txt上读取数据
                ps.write(b);                                        //将数据写到b.txt上
            }
            
            in.close();
            ps.close();

###22.13_IO流(修改标准输入输出流拷贝图片)(了解)
        System.setIn(new FileInputStream("IO图片.png"));        //改变标准输入流
        System.setOut(new PrintStream("copy.png"));         //改变标准输出流
        
        InputStream is = System.in;                            //获取标准输入流
        PrintStream ps = System.out;                        //获取标准输出流
        
        int len;
        byte[] arr = new byte[1024 * 8];
        
        while((len = is.read(arr)) != -1) {
            ps.write(arr, 0, len);
        }
        
        is.close();
        ps.close();

###22.14_IO流(两种方式实现键盘录入)(了解)
* A:BufferedReader的readLine方法。
    * BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
* B:Scanner

###22.15_IO流(Properties的概述和作为Map集合的使用)(了解)
* A:Properties的概述
    * Properties 类表示了一个持久的属性集。
    * Properties 可保存在流中或从流中加载。
    * 属性列表中每个键及其对应值都是一个字符串。 
* B:案例演示
    * Properties作为Map集合的使用
    
###22.16_IO流(Properties的特殊功能使用)(了解)
* A:Properties的特殊功能
    * public Object setProperty(String key,String value)
    * public String getProperty(String key)
    * public Enumeration<String> stringPropertyNames()
* B:案例演示
    * Properties的特殊功能
    
###22.17_IO流(Properties的load()和store()功能)(了解)
* A:Properties的load()和store()功能
* B:案例演示
    * Properties的load()和store()功能