高级知识复习"/>
Java高级知识复习
1.字符流输入流输出流，实现文本文件的复制
package top.oneluckyguy.thread;import org.junit.Test;import java.io.*;/*** @author Liu Qingfeng* @create 2020-12-18----21:30*/
public class FileReaderWritertest {public static void main(String[] args) {File file = new File("hello.txt");//相较于当前工程下System.out.println(file.getAbsolutePath());}/*将文件读入到程序中，并输出到控制台。知识点：1.read()的理解，返回读入的一个字符，如果到达文件末尾就返回-12.异常的处理：为了保证流的资源一定关闭，最好使用try_catch_finally来捕获异常。* */@Testpublic void testFileReader() {FileReader fileReader = null;try {// 1.实例化File类的对象，并指明要操作的文件File file = new File("src//top//oneluckyguy//pro//hello.txt");//相较于当前Module下
// 2.提供具体的流fileReader = new FileReader(file);
// 3.数据的读入//read()返回读入的一个字符，如果达到文件末尾，返回-1/* 方式一int data = fileReader.read();while(data != -1){System.out.println((char)(data));data = fileReader.read();}*///方式二int data;while((data = fileReader.read()) != -1){System.out.println((char)data);}}catch (IOException e){e.printStackTrace();}finally {//4.流的关闭if (fileReader != null){try {fileReader.close();}catch (IOException e){e.printStackTrace();}}}}@Testpublic void testFileReader1() throws IOException {FileReader fileReader = null;try {//1.File类的实例化File file = new File("src//top//oneluckyguy//pro//hello.txt");//2.FileReader流的实例化fileReader = new FileReader(file);//3.读入的操作//read(char[] cbuffer):返回每次读入cbuffer数组中的字符个数，如果达到文件末尾就返回-1char[] cbuffer = new char[5];int len;while ((len = fileReader.read(cbuffer)) != -1 ){//方式一// 如果是len.length输出为helloworld123ld,123会把world中的前三个字母覆盖，但是后三个不会覆盖，还是输出/*for (int i = 0; i < len; i++) {//这里是小于len不是小于len.length。System.out.println(cbuffer[i]);}*///方式二String string = new String(cbuffer,0,len);//如果这里不加0和len也会出现上面的错误System.out.println(string);}} catch (IOException e) {e.printStackTrace();} finally {if (fileReader != null){try {fileReader.close();} catch (IOException e) {e.printStackTrace();}}}}/** 从内存中写出数据到硬盘的文件里* */@Testpublic void testFileWriter() {FileWriter fileWriter = null;try {
// 1.提供File类的对象指明要写出的文件File file = new File("src//top//oneluckyguy//pro//hello1.txt");
// 2.提供FileWriter的对象,用于数据的写出fileWriter = new FileWriter(file,true);//加上true表示在原有文件上追加内容
// 3.写出操作fileWriter.write("I have a dream\n");fileWriter.write("You are beautiful");
// 4.流的关闭} catch (IOException e) {e.printStackTrace();} finally {try {if (fileWriter != null){fileWriter.close();}} catch (IOException e) {e.printStackTrace();}}}/** 实现文件的复制* */@Testpublic void testImgWriter(){FileWriter fileWriter = null;FileReader fileReader = null;try {
// 1.创建File对象，指明要对如和写出的文件File fileR = new File("src//top//oneluckyguy//pro//2.png");File fileW = new File("src//top//oneluckyguy//pro//3.png");
// 2.创建输入流和输出流的对象fileReader = new FileReader(fileR);fileWriter = new FileWriter(fileW);
// 3.数据的读入和写出操作char[] cbuffer = new char[5];int len;while ((len = fileReader.read(cbuffer)) != -1){for (int i = 0; i < len; i++) {fileWriter.write(cbuffer[i]);}}} catch (IOException e) {e.printStackTrace();} finally {try {if (fileWriter != null)fileWriter.close();} catch (IOException e) {e.printStackTrace();}try {if (fileReader != null)fileReader.close();} catch (IOException e) {e.printStackTrace();}}}}
2.字节流输入输出流实现图片复制
package top.oneluckyguy.io;import org.junit.Test;import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;/*** @author Liu Qingfeng* @create 2020-12-19----15:11* 测试FileInputStream 和FileOutputStream的使用* 结论：* 对于文本文件使用字符流处理(.txt .doc .c .cpp .java)* 对于非文本文件使用字节流处理(视频 音频 .ppt)*/
public class FileInputOutputStreamTest {//使用字节流处理文本文件是可能出现乱码的@Testpublic void testFileInputStream(){FileInputStream fileInputStream = null;try {//1.造文件File file = new File("hello.txt");//2.造流fileInputStream = new FileInputStream(file);//3.读数据byte[] cbuffer = new byte[5];int len = 0;while((len = fileInputStream.read(cbuffer)) != -1){String str = new String(cbuffer,0,len);System.out.println(str);}} catch (IOException e) {e.printStackTrace();} finally {if (fileInputStream != null){try {fileInputStream.close();} catch (IOException e) {e.printStackTrace();}}}}@Testpublic void testInputOutputStream(){FileInputStream fileInputStream = null;FileOutputStream fileOutputStream = null;try {//1.造文件File fileI = new File("2.png");File fileO = new File("3.png");//2.造流fileInputStream = new FileInputStream(fileI);fileOutputStream = new FileOutputStream(fileO);//3.读写的过程byte[] buffer = new byte[5];int len;while((len = fileInputStream.read(buffer)) != -1){fileOutputStream.write(buffer,0,len);}} catch (IOException e) {e.printStackTrace();} finally {try {if(fileOutputStream != null){fileOutputStream.close();}} catch (IOException e) {e.printStackTrace();}try {if (fileInputStream != null){fileInputStream.close();}} catch (IOException e) {e.printStackTrace();}}}//指定路径下文件的复制public void copyFile(String srcPath,String destPath){FileInputStream fileInputStream = null;FileOutputStream fileOutputStream = null;try {//1.造文件File fileI = new File(srcPath);File fileO = new File(destPath);//2.造流fileInputStream = new FileInputStream(fileI);fileOutputStream = new FileOutputStream(fileO);//3.读写的过程byte[] buffer = new byte[1024];int len;while((len = fileInputStream.read(buffer)) != -1){fileOutputStream.write(buffer,0,len);}} catch (IOException e) {e.printStackTrace();} finally {try {if(fileOutputStream != null){fileOutputStream.close();}} catch (IOException e) {e.printStackTrace();}try {if (fileInputStream != null){fileInputStream.close();}} catch (IOException e) {e.printStackTrace();}}}@Testpublic void testCopyFile(){long start = System.currentTimeMillis();copyFile("2.png","4.png");long end = System.currentTimeMillis();System.out.println("复制花费的时间："+ (end - start));}
}
3.缓冲流实现文件复制，速度与节点流比较是否更快。
package top.oneluckyguy.io;import org.junit.Test;import java.io.*;/*** @author Liu Qingfeng* @create 2020-12-19----16:44*/
/*
* 实现非文本文件的复制
* */
public class BufferedTest {public void BufferedStreamTest (String srcPath,String destPath){FileInputStream fileInputStream = null;FileOutputStream fileOutputStream = null;try {//1.造文件File filei = new File(srcPath);File fileo = new File(destPath);//2.造节点流fileInputStream = new FileInputStream(filei);fileOutputStream = new FileOutputStream(fileo);
// 3.造缓冲流BufferedInputStream bufferedInputStream = new BufferedInputStream(fileInputStream);BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(fileOutputStream);//4.操作byte[] buffer= new byte[1024];int len;while((len = bufferedInputStream.read(buffer)) != -1){bufferedOutputStream.write(buffer,0,len);}} catch (IOException e) {e.printStackTrace();} finally {//5.关闭流if (fileInputStream != null){try {fileInputStream.close();} catch (IOException e) {e.printStackTrace();}}if (fileOutputStream != null){try {fileOutputStream.close();} catch (IOException e) {e.printStackTrace();}}}}@Testpublic void fileBufferedCopyTest(){long start = System.currentTimeMillis();BufferedStreamTest("2.png","4.png");long end = System.currentTimeMillis();System.out.println("复制花费的时间："+ (end - start));}
}
4.转换流的使用
InputStreamReader
OutputStreamwriter
package top.oneluckyguy.io;import org.junit.Test;import java.io.*;/*** @author Liu Qingfeng* @create 2020-12-19----20:39* 处理流二：* 1.转换流：输入字符流* InputStreamReader 将一个字节的输入流转换为字符的输入流* OutputStreamWriter 将一个字符的输出流转化为字节的输出流* 2.作用：提供字节流与字符流之间的转换* 3.解码： 字节 字节数组----->字符数组 字符串* 编码： 字符数组 字符串----->字节 字节数组* 4.字符集***/
public class InputStreamReaderTest {@Testpublic void test(){InputStreamReader inputStreamReader = null;try {File file = new File("hello.txt");FileInputStream fileInputStream = new FileInputStream(file);inputStreamReader = new InputStreamReader(fileInputStream,"UTF-8");char[] cbuffer = new char[5];int len;while((len = inputStreamReader.read(cbuffer)) != -1){String str = new String(cbuffer,0,len);System.out.println(str);}} catch (IOException e) {e.printStackTrace();} finally {if (inputStreamReader != null){try {inputStreamReader.close();} catch (IOException e) {e.printStackTrace();}}}}/** 综合使用InputStreamReader 和OutputStreamWriter* 把utf-8文件以utf-8格式读入以gbk格式输出* */@Testpublic void testAll(){InputStreamReader inputStreamReader = null;OutputStreamWriter outputStreamWriter = null;try {File fileI = new File("hello.txt");File fileO = new File("rehello.txt");FileInputStream fileInputStream = new FileInputStream(fileI);FileOutputStream fileOutputStream = new FileOutputStream(fileO);inputStreamReader = new InputStreamReader(fileInputStream,"utf-8");outputStreamWriter = new OutputStreamWriter(fileOutputStream,"gbk");char[] cbuffer = new char[5];int len;while((len = inputStreamReader.read(cbuffer)) != -1){outputStreamWriter.write(cbuffer,0,len);}} catch (IOException e) {e.printStackTrace();} finally {if (inputStreamReader != null){try {inputStreamReader.close();} catch (IOException e) {e.printStackTrace();}}if (outputStreamWriter != null){try {outputStreamWriter.close();} catch (IOException e) {e.printStackTrace();}}}}
}5.对象流
1.对String字符串进行序列化和反序列化的输入输出
package top.oneluckyguy.objectIO;import org.junit.Test;import java.io.*;/*** @author Liu Qingfeng* @create 2020-12-20----15:29* 对象流的使用：* 1.ObjectInputStream和ObjectOutputStream* 2.作用：用于存储和读取基本数据类型数据或对象的处理流，* 3.要想一个Java对象是可序列化的，需要满足相应的要求：详见Person类*/
public class ObjectInputOutputStreamTest {/** 序列化过程，将内存中的Java对象保存到磁盘中或者通过网络传播出去* 使用ObjectOutputStram实现* */@Testpublic void testObjectOutputStream(){ObjectOutputStream objectOutputStream = null;try {objectOutputStream = new ObjectOutputStream(new FileOutputStream("hello.data"));objectOutputStream.writeObject(new String("坂井泉水"));objectOutputStream.flush();//把缓存中的数据刷新出去} catch (IOException e) {e.printStackTrace();} finally {if (objectOutputStream != null){try {objectOutputStream.close();} catch (IOException e) {e.printStackTrace();}}}}/** 反序列化，将磁盘文件中的对象还原为内存中的一个Java对象* 需要使用ObjectInputStream* */@Testpublic void testObjectInputStream(){ObjectInputStream objectInputStream = null;String str = null;try {objectInputStream = new ObjectInputStream(new FileInputStream("hello.data"));Object obj = objectInputStream.readObject();str = (String) obj;System.out.println(str);} catch (IOException e) {e.printStackTrace();} catch (ClassNotFoundException e) {e.printStackTrace();} finally {if (objectInputStream != null){try {objectInputStream.close();} catch (IOException e) {e.printStackTrace();}}}}
}
2.对Objec对象的序列化和反序列化
①对象类
package top.oneluckyguy.objectIO;import java.io.Serializable;/*** @author Liu Qingfeng* @create 2020-12-20----15:51*/
public class Person implements Serializable {//这里如果不写UID系统会自动给你配一个UID，你序列化时用的UID必须和反序列化的UID一样//必须指定UID，如果不指定，对当前类修改的时候就会变化public static final long serialVersionUID = 12L;private String name;private int age;public Person(String name,int age){this.name = name;this.age = age;}public Person() {}@Overridepublic String toString() {return "Person{" +"name='" + name + '\'' +", age=" + age +'}';}public void setAge(int age) {this.age = age;}public int getAge() {return age;}public void setName(String name) {this.name = name;}public String getName() {return name;}
}
②处理流
package top.oneluckyguy.objectIO;import org.junit.Test;
import java.io.*;/*** @author Liu Qingfeng* @create 2020-12-20----15:29* 对象流的使用：* 1.ObjectInputStream和ObjectOutputStream* 2.作用：用于存储和读取基本数据类型数据或对象的处理流，* 3.要想一个Java对象是可序列化的，需要满足相应的要求：详见Person类* 1.需要实现接口：Serializable* 2.当前类需要提供一个全局常量serialVersionUID* eg: public static final long serialVersionUID = -2228226523704288112L;* 3.除了当前Person类需要实现Serializable接口外还要保证其内部所有属性也必须是可序列化的。* （默认情况下，基本数据类型都是可序列化的，同时String类型也是可序列化的）* （如果Person类中有一个别的类Man作为Person类的参数，那么这个类Man也要可序列化实现Serializable接口和提供一个UID（这个UID和Person的不同））。* 补充：* ObjectOutputStream和ObjectInputStream不能序列化static和transient修饰的成员变量* （不会报编译错误，但是数据不会保存。）*/
public class ObjectInputOutputStreamTest {/** 序列化过程，将内存中的Java对象保存到磁盘中或者通过网络传播出去* 使用ObjectOutputStram实现* */@Testpublic void testObjectOutputStream(){ObjectOutputStream objectOutputStream = null;try {objectOutputStream = new ObjectOutputStream(new FileOutputStream("hello.data"));objectOutputStream.writeObject(new String("坂井泉水"));objectOutputStream.flush();//把缓存中的数据刷新出去objectOutputStream.writeObject(new Person("大黑摩季",18));objectOutputStream.flush();} catch (IOException e) {e.printStackTrace();} finally {if (objectOutputStream != null){try {objectOutputStream.close();} catch (IOException e) {e.printStackTrace();}}}}/** 反序列化，将磁盘文件中的对象还原为内存中的一个Java对象* 需要使用ObjectInputStream* */@Testpublic void testObjectInputStream(){ObjectInputStream objectInputStream = null;String str = null;Person person = null;try {objectInputStream = new ObjectInputStream(new FileInputStream("hello.data"));Object obj = objectInputStream.readObject();str = (String) obj;Object objects = objectInputStream.readObject();person = (Person) objects;System.out.println(str);System.out.println(person);} catch (IOException e) {e.printStackTrace();} catch (ClassNotFoundException e) {e.printStackTrace();} finally {if (objectInputStream != null){try {objectInputStream.close();} catch (IOException e) {e.printStackTrace();}}}}
}
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