序列化：把基本数据裂隙或对象写入数据源；
反序列化：把对象从数据源中还原回来。
package com.atguigu.java;
import org.junit.Test;
import java.io.*;
public class ObjectInputOutputStreamTest {
@Test
public void testObjectOutputStream(){
ObjectOutputStream oos = null;
try {
//1.
oos = new ObjectOutputStream(new FileOutputStream("object.dat"));//创建一个文件object.dat
//2.
oos.writeObject(new String("我爱北京天安门"));//把"我爱北京天安门"写到文件中，序列化
oos.flush();//刷新操作,把缓冲区的内容强制的写出
oos.writeObject(new Person("王铭",23));
oos.flush();
oos.writeObject(new Person("张学良",23,1001,new Account(5000)));
oos.flush();
} catch (IOException e) {
e.printStackTrace();
} finally {
if(oos != null){
//3.关闭流
try {
oos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
@Test
public void testObjectInputStream(){
ObjectInputStream ois = null;
try {
ois = new ObjectInputStream(new FileInputStream("object.dat"));//读取文件"object.dat"内容
Object obj = ois.readObject();//反序列化，读到一个java对象
String str = (String) obj;
//按顺序读 按顺序反序列化
Person p = (Person) ois.readObject();
Person p1 = (Person) ois.readObject();
System.out.println(str);
System.out.println(p);
System.out.println(p1);
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} finally {
if(ois != null){
try {
ois.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
class Person implements Serializable
package com.atguigu.java;
import java.io.Serializable;
public class Person implements Serializable{
public static final long serialVersionUID = 475463534532L;//long类型的随便写一个
private String name;
private int age;
private int id;
private Account acct;//
public Person(String name, int age, int id) {
this.name = name;
this.age = age;
this.id = id;
}
public Person(String name, int age, int id, Account acct) {
this.name = name;
this.age = age;
this.id = id;
this.acct = acct;
}
@Override
public String toString() {
return "Person{" +
"name='" + name + ''' +
", age=" + age +
", id=" + id +
", acct=" + acct +
'}';
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public Person(String name, int age) {
this.name = name;
this.age = age;
}
public Person() {
}
}
class Account implements Serializable{
public static final long serialVersionUID = 4754534532L;
private double balance;
@Override
public String toString() {
return "Account{" +
"balance=" + balance +
'}';
}
public double getBalance() {
return balance;
}
public void setBalance(double balance) {
this.balance = balance;
}
public Account(double balance) {
this.balance = balance;
}
}
随机存取文件流
RandomAccessFile实现数据的读写、插入操作
RandomAccessFileTest.java
package com.atguigu.java;
import org.junit.Test;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
public class RandomAccessFileTest {
@Test
public void test1() {
RandomAccessFile raf1 = null;
RandomAccessFile raf2 = null;
try {
//1.造对象
//↓第一个参数，读进的文件的位置，第二个参数指定访问文件的方式
raf1 = new RandomAccessFile(new File("爱情与友情.jpg"),"r");
raf2 = new RandomAccessFile(new File("爱情与友情1.jpg"),"rw");
//2.读写过程
byte[] buffer = new byte[1024];
int len;
while((len = raf1.read(buffer)) != -1){//read(buffer)读出数据写到buffer中，并返回读了多少字节数据
raf2.write(buffer,0,len);//把buffer中的数据写出去，写到raf2中。
}
} catch (IOException e) {
e.printStackTrace();
} finally {
//3.关闭流
if(raf1 != null){
try {
raf1.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(raf2 != null){
try {
raf2.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
@Test
public void test2() throws IOException {
//如果RandomAccessFile作为输出流时，写出到的文件如果不存在，则在执行过程中自动创建。
//如果写出到的文件存在，则会对原有文件内容进行覆盖。（默认情况下，从头覆盖）
RandomAccessFile raf1 = new RandomAccessFile("hello.txt","rw");
raf1.seek(3);//将指针调到角标为3的位置
raf1.write("xyz".getBytes());//实现覆盖
//write里面要传入byte数组，getbyte就是获得数组；
// 讲string的时候说过，通过getBytes()进行string和字节数组之间的转换
raf1.close();
//操作后hello.txt中 abcdefg→→→abcxyzg
}
@Test
public void test3() throws IOException {
RandomAccessFile raf1 = new RandomAccessFile("hello.txt","rw");
raf1.seek(3);//将指针调到角标为3的位置
//保存指针3后面的所有数据到StringBuilder中
StringBuilder builder = new StringBuilder((int) new File("hello.txt").length());
byte[] buffer = new byte[20];
int len;
//buffer数组长20字节，读取raf1中的20字节到buffer中，然后在添加到builder中，如果读完了，是空的，则返回-1
while((len = raf1.read(buffer)) != -1){
builder.append(new String(buffer,0,len)) ;
}
//调回指针，写入“xyz”
raf1.seek(3);
raf1.write("xyz".getBytes());
//将StringBuilder中的数据写入到文件中
raf1.write(builder.toString().getBytes());
raf1.close();
//操作后hello.txt中 abcdefgh→→→abcxyzdefgh
}
}
NIO介绍及NIO2中Path、Paths、Files的介绍
1、找到相应的jar吧 ctrl+c复制jar包
2、新建一个directory目录，命名为lib或者libs
3、点击lib，ctrl+v粘贴jar包
4、add as library，就可以作为api使用了
5、就可以在程序中调用jar包中的类了
