2019独角兽企业重金招聘Python工程师标准>>> 
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 Vectorv = 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 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();
package com.heima.otherio;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.SequenceInputStream;
import java.util.Enumeration;
import java.util.Vector;
public class Demo01_SequenceInputStream {
/**
* @param args
* 整合两个输入流
* SequenceInputStream(InputStream s1, InputStream s2)
* 整合多个输入流
* SequenceInputStream(Enumeration e)
* @throws IOException
*/
public static void main(String[] args) throws IOException {
//demo1();
//demo2();
FileInputStream fis1 = new FileInputStream("a.txt");
FileInputStream fis2 = new FileInputStream("b.txt");
FileInputStream fis3 = new FileInputStream("c.txt");
Vector v = new Vector<>(); //创建集合对象
v.add(fis1); //将流对象存储进来
v.add(fis2);
v.add(fis3);
Enumeration en = v.elements();
SequenceInputStream sis = new SequenceInputStream(en); //将枚举中的输入流整合成一个
FileOutputStream fos = new FileOutputStream("d.txt");
int b;
while((b = sis.read()) != -1) {
fos.write(b);
}
sis.close();
fos.close();
}
public static void demo2() throws FileNotFoundException, IOException {
FileInputStream fis1 = new FileInputStream("a.txt");
FileInputStream fis2 = new FileInputStream("b.txt");
SequenceInputStream sis = new SequenceInputStream(fis1, fis2);
FileOutputStream fos = new FileOutputStream("c.txt");
int b;
while((b = sis.read()) != -1) {
fos.write(b);
}
sis.close(); //sis在关闭的时候,会将构造方法中传入的流对象也都关闭
fos.close();
}
public static void demo1() throws FileNotFoundException, IOException {
FileInputStream fis1 = new FileInputStream("a.txt"); //创建字节输入流关联a.txt
FileOutputStream fos = new FileOutputStream("c.txt"); //创建字节输出流关联c.txt
int b1;
while((b1 = fis1.read()) != -1) { //不断的在a.txt上读取字节
fos.write(b1); //将读到的字节写到c.txt上
}
fis1.close(); //关闭字节输入流
FileInputStream fis2 = new FileInputStream("b.txt");
int b2;
while((b2 = fis2.read()) != -1) {
fos.write(b2);
}
fis2.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();
package com.heima.otherio;
import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
public class Demo02_ByteArrayOutputStream {
/**
* @param args
* ByteArrayOutputStream
* 内存输出流
*
* FileInputStream读取中文的时候出现了乱码
*
* 解决方案
* 1,字符流读取
* 2,ByteArrayOutputStream
* @throws IOException
*/
public static void main(String[] args) throws IOException {
//demo1();
FileInputStream fis = new FileInputStream("e.txt");
ByteArrayOutputStream baos = new ByteArrayOutputStream(); //在内存中创建了可以增长的内存数组
int b;
while((b = fis.read()) != -1) {
baos.write(b); //将读取到的数据逐个写到内存中
}
//byte[] arr = baos.toByteArray(); //将缓冲区的数据全部获取出来,并赋值给arr数组
//System.out.println(new String(arr));
System.out.println(baos.toString()); //将缓冲区的内容转换为了字符串,在输出语句中可以省略调用toString方法
fis.close();
}
public static void demo1() throws FileNotFoundException, IOException {
FileInputStream fis = new FileInputStream("e.txt");
byte[] arr = new byte[3];
int len;
while((len = fis.read(arr)) != -1) {
System.out.println(new String(arr,0,len));
}
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()
package com.heima.otherio;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
public class Demo08_RandomAccessFile {
/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
RandomAccessFile raf = new RandomAccessFile("g.txt", "rw");
//raf.write(97);
//int x = raf.read();
//System.out.println(x);
raf.seek(0); //在指定位置设置指针
raf.write(98);
raf.close();
}
}
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(); } }
-
package com.heima.otherio;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import com.heima.bean.Person;
public class Demo03_ObjectOutputStream {
/**
* @param args
* 序列化:将对象写到文件上
* @throws IOException
*/
public static void main(String[] args) throws IOException {
//demo1();
Person p1 = new Person("张三", 23);
Person p2 = new Person("李四", 24);
Person p3 = new Person("王五", 25);
Person p4 = new Person("赵六", 26);
ArrayList list = new ArrayList<>();
list.add(p1);
list.add(p2);
list.add(p3);
list.add(p4);
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("e.txt"));
oos.writeObject(list); //把整个集合对象一次写出
oos.close();
}
public static void demo1() throws IOException, FileNotFoundException {
Person p1 = new Person("张三", 23);
Person p2 = new Person("李四", 24);
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("e.txt"));
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(); } }
-
package com.heima.otherio;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.util.ArrayList;
import com.heima.bean.Person;
public class Demo04_ObjectInputStream {
/**
* @param args
* @throws IOException
* @throws FileNotFoundException
* @throws ClassNotFoundException
* ObjectInputStream
* 对象输入流,反序列化
*/
public static void main(String[] args) throws FileNotFoundException, IOException, ClassNotFoundException {
//demo1();
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("e.txt"));
ArrayList list = (ArrayList) ois.readObject(); //将集合对象一次读取
for (Person person : list) {
System.out.println(person);
}
ois.close();
}
public static void demo1() throws IOException, FileNotFoundException,
ClassNotFoundException {
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("e.txt"));
Person p1 = (Person) ois.readObject();
Person p2 = (Person) ois.readObject();
//Person p3 = (Person) ois.readObject(); //当文件读取到了末尾时出现EOFException
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 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")); ArrayListlist = (ArrayList )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();
-
package com.heima.otherio;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
public class Demo09_Data {
/**
* @param args
* @throws IOException
* 00000000 00000000 00000011 11100101 int类型997
* 11100101
* 00000000 00000000 00000000 11100101
*/
public static void main(String[] args) throws IOException {
//demo1();
//demo2();
//demo3();
DataInputStream dis = new DataInputStream(new FileInputStream("h.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();
}
public static void demo3() throws FileNotFoundException, IOException {
DataOutputStream dos = new DataOutputStream(new FileOutputStream("h.txt"));
dos.writeInt(997);
dos.writeInt(998);
dos.writeInt(999);
dos.close();
}
public static void demo2() throws FileNotFoundException, IOException {
FileInputStream fis = new FileInputStream("h.txt");
int x = fis.read();
int y = fis.read();
int z = fis.read();
System.out.println(x);
System.out.println(y);
System.out.println(z);
fis.close();
}
public static void demo1() throws FileNotFoundException, IOException {
FileOutputStream fos = new FileOutputStream("h.txt");
fos.write(997);
fos.write(998);
fos.write(999);
fos.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();
package com.heima.otherio;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintStream;
import java.io.PrintWriter;
import com.heima.bean.Person;
public class Demo05_PrintStream {
/**
* @param args
* @throws IOException
* PrintStream和PrintWriter分别是打印的字节流和字符流
* 只操作数据目的的
*/
public static void main(String[] args) throws IOException {
//demo1();
PrintWriter pw = new PrintWriter(new FileOutputStream("f.txt"),true);
//pw.println(97); //自动刷出功能只针对的是println方法
//pw.write(97);
pw.print(97);
pw.println(97);
pw.close();
}
public static void demo1() {
System.out.println("aaa");
PrintStream ps = System.out; //获取标注输出流
ps.println(97); //底层通过Integer.toString()将97转换成字符串并打印
ps.write(97); //查找码表,找到对应的a并打印
Person p1 = new Person("张三", 23);
ps.println(p1); //默认调用p1的toString方法
Person p2 = null; //打印引用数据类型,如果是null,就打印null,如果不是null就打印对象的toString方法
ps.println(p2);
ps.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();
package com.heima.otherio;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintStream;
public class Demo06_SystemInOut {
/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
//demo1();
System.setIn(new FileInputStream("a.txt")); //改变标准输入流
System.setOut(new PrintStream("b.txt")); //改变标注输出流
InputStream is = System.in; //获取标准的键盘输入流,默认指向键盘,改变后指向文件
PrintStream ps = System.out; //获取标准输出流,默认指向的是控制台,改变后就指向文件
int b;
while((b = is.read()) != -1) {
ps.write(b);
}
//System.out.println(); //也是一个输出流,不用关,因为没有和硬盘上的文件产生关联的管道
is.close();
ps.close();
}
public static void demo1() throws IOException {
InputStream is = System.in;
int x = is.read();
System.out.println(x);
is.close();
InputStream is2 = System.in;
int y = is2.read();
System.out.println(y);
}
}
package com.heima.otherio;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Scanner;
public class Demo07_SystemIn {
/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
/*BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); //InputStreamReader转换流
String line = br.readLine();
System.out.println(line);
br.close();*/
Scanner sc = new Scanner(System.in);
String line = sc.nextLine();
System.out.println(line);
sc.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();
package com.heima.test;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintStream;
public class Test2 {
/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
System.setIn(new FileInputStream("双元.jpg")); //改变标准输入流
System.setOut(new PrintStream("copy.jpg")); //改变标准输出流
InputStream is = System.in;
PrintStream ps = System.out;
byte[] arr = new byte[1024];
int len;
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 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
package com.heima.otherio;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Enumeration;
import java.util.Properties;
public class Demo10_Properties {
/**
* @param args
* Properties是Hashtable的子类
* @throws IOException
* @throws FileNotFoundException
*/
public static void main(String[] args) throws FileNotFoundException, IOException {
//demo1();
//demo2();
Properties prop = new Properties();
prop.load(new FileInputStream("config.properties")); //将文件上的键值对读取到集合中
prop.setProperty("tel", "18912345678");
prop.store(new FileOutputStream("config.properties"), null);//第二个参数是对列表参数的描述,可以给值,也可以给null
System.out.println(prop);
}
public static void demo2() {
Properties prop = new Properties();
prop.setProperty("name", "张三");
prop.setProperty("tel", "18912345678");
//System.out.println(prop);
Enumeration en = (Enumeration) prop.propertyNames();
while(en.hasMoreElements()) {
String key = en.nextElement(); //获取Properties中的每一个键
String value = prop.getProperty(key); //根据键获取值
System.out.println(key + "="+ value);
}
}
public static void demo1() {
Properties prop = new Properties();
prop.put("abc", 123);
System.out.println(prop);
}
}
-
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)
package com.heima.test;
import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
public class Test1 {
/**
* @param args
* 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)
*
* 分析:
* 1,reda(byte[] b)是字节输入流的方法,创建FileInputStream,关联a.txt
* 2,创建内存输出流,将读到的数据写到内存输出流中
* 3,创建字节数组,长度为5
* 4,将内存输出流的数据全部转换为字符串打印
* 5,关闭输入流
* @throws IOException
*/
public static void main(String[] args) throws IOException {
//1,reda(byte[] b)是字节输入流的方法,创建FileInputStream,关联a.txt
FileInputStream fis = new FileInputStream("a.txt");
//2,创建内存输出流,将读到的数据写到内存输出流中
ByteArrayOutputStream baos = new ByteArrayOutputStream();
//3,创建字节数组,长度为5
byte[] arr = new byte[5];
int len;
while((len = fis.read(arr)) != -1) {
baos.write(arr, 0, len);
//System.out.println(new String(arr,0,len));
}
//4,将内存输出流的数据全部转换为字符串打印
System.out.println(baos); //即使没有调用,底层也会默认帮我们调用toString()方法
//5,关闭输入流
fis.close();
}
}