本文介绍了 Java 中 IO 流的应用实例，包括打印流、序列流、随机访问文件流、内存流等，演示了文件合并、分割、序列化、反序列化等操作，并通过具体代码实现了学生信息的输入、处理和保存。
import java.io.*;
class Demo1
{
public static void main(String[] args)throws IOException
{
/*
PrintStream:打印流，具备字节输出流的基本功能，添加了打印功能
是一个可以向目的写入的输出流
目的：File
字符串形式的路径
字节输出流
*/
PrintStream ps = new PrintStream("tt.txt");
//一次写入一个字节
//ps.write(353);//00000000 00000000 00000001 01100001 把低8位的一个字节写入
ps.println(353);//按照数据原样儿写入，也就是数据的表现形式，内部使用了转成字符串的功能，String.valueOf()
ps.write(String.valueOf(353).getBytes());
}
}
import java.io.*;
class Demo2
{
public static void main(String[] args) throws IOException
{
/*
PrintWriter:字符打印流,字符输出流的基本功能都具备
目的：File
字符串形式的路径
字节输出流
字符数出流
*/
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
//PrintWriter pw = new PrintWriter(System.out,true);
PrintWriter pw2 = new PrintWriter(new FileWriter("t.txt"),true);
String line = null;
while((line = br.readLine())!=null)
{
if("over".equals(line))
break;
pw2.println(line);
//pw.flush();
}
}
}
//序列流:SequenceInputStream
import java.io.*;
import java.util.*;
class Demo3
{
public static void main(String[] args) throws IOException
{ /*
FileInputStream fis1= new FileInputStream("Demo1.java");
FileInputStream fis2= new FileInputStream("Demo2.java");
FileInputStream fis3= new FileInputStream("Demo3.java");
Vector<FileInputStream> v= new Vector<FileInputStream>();
v.add(fis1);
v.add(fis2);
v.add(fis3);
Enumeration<FileInputStream> en = v.elements();*/
ArrayList<FileInputStream> list = new ArrayList<FileInputStream>();
for(int i=1;i<=3;i++)
{
list.add(new FileInputStream("Demo"+i+".java"));
}
Enumeration<FileInputStream> en = Collections.enumeration(list);
SequenceInputStream sis = new SequenceInputStream(en);
FileOutputStream fos = new FileOutputStream("hebing2.java");
byte[] b = new byte[1024];
int len = 0;
while((len = sis.read(b))!=-1)
{
fos.write(b,0,len);
}
sis.close();
fos.close();
}
}
//分割文件
import java.io.*;
import java.util.*;
class Demo4
{
public static void main(String[] args)throws IOException
{
File file = new File("C:\\Users\\qq\\Desktop\\ok.jpg");
splitFile(file);
}
//分割文件
public static void splitFile(File file)throws IOException
{
if(!file.isFile())
{
System.out.println("不是文件");
return;
}
//创建存储被分割出来的文件的目录
File dir = new File("fenge");
if(!dir.exists())
dir.mkdir();
FileInputStream fis = new FileInputStream(file);
FileOutputStream fos = null;
byte[] arr = new byte[1024*1024*2];
int len = 0;
int num = 1;
while((len = fis.read(arr))!=-1)
{
fos = new FileOutputStream(new File(dir,(num++)+".suipian"));
fos.write(arr,0,len);
}
//这几个被分割出来的文件上传之后，使用者不知道文件类型和一共有
//几个分割出的文件，应该把这些信息以配置文件的形式告诉使用者
Properties pro = new Properties();
pro.setProperty("filetype",file.getName());
pro.setProperty("fileNumber",Integer.toString(--num));
fos = new FileOutputStream(new File(dir,"config.properties"));
pro.store(fos," ");
fis.close();
fos.close();
}
}
import java.io.*;
class Person implements Serializable//标记接口
{
static final long serialVersionUID = 42L;
private /*static*/ String name;//被静态修饰的成员不参与序列化
private /*transient*/ int age; //瞬态的成员不参与序列化
public Person(){}
public Person(String name,int age)
{
this.name = name;
this.age = age;
}
public String getName()
{
return this.name;
}
public int getAge()
{
return this.age;
}
}
class Demo5
{
public static void main(String[] args)throws IOException,ClassNotFoundException
{
//writeObject();
readObject();
}
//反序列化
//对象是依赖于其所属的类的，有那个class才会有对象
public static void readObject()throws IOException,ClassNotFoundException
{
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("obj.txt"));
Person person = (Person)ois.readObject();//5964614836505496678 -2747677651716560467
System.out.println(person.getName()+","+person.getAge());
}
//写入对象
//序列化:把一个对象写入到一个目的--对象的持久化
public static void writeObject()throws IOException
{
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("obj.txt"));
oos.writeObject(new Person("lisi",23));//5964614836505496678 Person.class
oos.close();
}
}
import java.io.*;
class Demo6
{
public static void main(String[] args)throws IOException
{
/*
RandomeAccessFile:
随机访问文件的流类
只能访问文件
内部既有字节输入流也有字节输出流
内部定义了一个字节数组，并通过指针操作该数组，所以能随机访问
*/
//writeFile();
//readFile();
rw();
}
public static void rw()throws IOException
{
RandomAccessFile raf = new RandomAccessFile("rw.txt","rw");
raf.seek(30);
raf.writeUTF("你好");
long index = raf.getFilePointer();
System.out.println("index="+index);
raf.seek(30);
String ss = raf.readUTF();
System.out.println(ss);
}
public static void readFile()throws IOException
{
RandomAccessFile raf = new RandomAccessFile("temp.txt","r");
byte[] arr = new byte[4];
int len = 0;
len = raf.read(arr);
int age = raf.readInt();
System.out.println(new String(arr,0,len)+","+age);
long index = raf.getFilePointer();
System.out.println("index="+index);
raf.seek(15);
len = raf.read(arr);
age = raf.readInt();
System.out.println(new String(arr,0,len)+","+age);
}
public static void writeFile()throws IOException
{
//文件不存在会自动创建
RandomAccessFile raf = new RandomAccessFile("temp.txt","rw");
raf.write("刘能".getBytes());
raf.writeInt(58);
long index = raf.getFilePointer();//得到指针指向的位置
raf.seek(15);
raf.write("赵四".getBytes());
raf.writeInt(56);
index = raf.getFilePointer();
System.out.println("index="+index);
}
}
import java.io.*;
class Demo7
{
public static void main(String[] args)throws IOException
{
/*
用于操作基本数据类型的流类
DataInputStream DataOutputStream
*/
writeData();
readData();
}
public static void readData()throws IOException
{
DataInputStream dis = new DataInputStream(new FileInputStream("data.txt"));
int a = dis.readInt();
boolean boo = dis.readBoolean();
double d = dis.readDouble();
System.out.println(a+","+boo+","+d);
}
public static void writeData()throws IOException
{
DataOutputStream dos = new DataOutputStream(new FileOutputStream("data.txt"));
dos.writeInt(34);
dos.writeBoolean(false);
dos.writeDouble(45.56);
dos.close();
}
}
import java.io.*;
class Demo8
{
public static void main(String[] args)throws IOException
{
/*
内存流：
ByteArrayInputStream:内部有一个字节数组
ByteArrayOutputStream: 内部有一个字节数组，直接写入了自己内部的字节数组了
*/
ByteArrayInputStream du = new ByteArrayInputStream("owieurwoeir".getBytes());
ByteArrayOutputStream xie = new ByteArrayOutputStream();
byte[] arr = new byte[1024];
int len = 0;
while((len =du.read(arr))!=-1)
{
xie.write(arr,0,len);
}
System.out.println(new String(xie.toByteArray()));
}
}
import java.io.*;
import java.util.*;
import java.text.*;
class Demo10
{
public static void main(String[] args) throws IOException
{
try
{
int[] arr = new int[3];
System.out.println(arr[3]);
}
catch (Exception e)
{
Date d = new Date();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd E HH:mm:ss");
String ss = sdf.format(d);
PrintStream ps = new PrintStream("bug.txt");
ps.println(ss);
System.setOut(ps);
e.printStackTrace(System.out);
}
}
}
/*
二:有五个学生，每个学生有3门课的成绩，
从键盘输入以上数据（包括姓名，三门课成绩），
输入的格式：如：zhagnsan，30，40，60计算出总成绩，
并把学生的信息和计算出的总分数高低顺序存放在磁盘文件"stud.txt"中。
1:描述一下学生
2:定义个操作学生的工具类
*/
import java.io.*;
import java.util.*;
class Student implements Comparable<Student>
{
private String name;
private int math,china,eng;
private int sum;
public Student(){}
public Student(String name,int math,int china,int eng)
{
this.name =name;
this.math = math;
this.china = china;
this.eng = eng;
sum = math+china+eng;
}
public int compareTo(Student stu)
{
int num = this.sum-stu.sum;
return num==0?this.name.compareTo(stu.name):num;
}
public int getSum()
{
return this.sum;
}
public int getMath()
{
return this.math;
}
public int getChina()
{
return this.china;
}
public int getEng()
{
return this.eng;
}
public String toString()
{
return "Student["+name+","+math+","+china+","+eng+"]";
}
}
//操作学生的工具类
class StuTool
{
public static Set<Student> getStudents()
{
return getStudents(null);
}
//读取键盘录入的学生信息，并存入集合
public static Set<Student> getStudents(Comparator<Student> com)throws IOException
{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
TreeSet<Student> students;
if(com!=null)
students = new TreeSet<Student>(com);
else
students = new TreeSet<Student>();
String line = null;
for(int i=1;i<=3;i++)
{
System.out.println("请输入第"+i+"个学员的信息");
line = br.readLine();
String[] arr = line.split(",");
Student stu = new Student(arr[0],Integer.parseInt(arr[1]),Integer.parseInt(arr[2]),Integer.parseInt(arr[3]));
students.add(stu);
}
return students;
}
//把学员信息存入文件
public static void saveToFile(Set<Student> students)throws IOException
{
BufferedWriter bw = new BufferedWriter(new FileWriter("stud.txt"));
for(Student stu:students)
{
bw.write(stu.toString()+"\t");
bw.write(""+stu.getSum());
bw.newLine();
bw.flush();
}
bw.close();
}
}
class Demo11
{
public static void main(String[] args) throws IOException
{
Comparator<Student> com = Collections.reverseOrder();
Set<Student> s = StuTool.getStudents(com);
StuTool.saveToFile(s);
}
}
import java.io.*;
class Demo12
{
public static void main(String[] args)throws IOException
{
//转换流的编码问题
//writeFile();
readFile();
}
public static void readFile()throws IOException
{
InputStreamReader isr = new InputStreamReader(new FileInputStream("gbk.txt"),"utf-8");
char[] ch = new char[10];
int len = 0;
len = isr.read(ch);
System.out.println(new String(ch,0,len));
}
public static void writeFile()throws IOException
{
OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("utf.txt"),"utf-8");
osw.write("你好");
osw.close();
}
}
/*
编码：家里有事，速回。----》电报文
byte[] getBytes()
使用平台的默认字符集将此 String 编码为 byte 序列
byte[] getBytes(String charsetName)
使用指定的字符集将此 String 编码为 byte 序列
解码：电报文-----》家里有事，速回。
String(byte[] bytes)
通过使用平台的默认字符集解码指定的 byte 数组，构造一个新的 String。
String(byte[] bytes, Charset charset)
通过使用指定的 charset 解码指定的 byte 数组，构造一个新的 String
编码编对了,解码就能解对
编码编错了，就不可能解对
*/
import java.util.*;
class Demo13
{
public static void main(String[] args)throws Exception
{
String ss ="你好";
byte[] b = ss.getBytes("gbk");
System.out.println(Arrays.toString(b));
//解码解错了
String str = new String(b,"ISO8859-1");
System.out.println(str);
//解决解码解错了的问题
byte[] arr = str.getBytes("ISO8859-1");
//使用gbk进行解码
String s = new String(arr);
System.out.println(s);
}
}
class Demo14
{
public static void main(String[] args)
{
String ss = "我的联通";
byte[] b = ss.getBytes();
for(byte num:b)
{
System.out.println(Integer.toBinaryString(num&255));
}
}
}
import java.io.*;
class Demo1
{
public static void main(String[] args)throws IOException
{
/*
PrintStream:打印流，具备字节输出流的基本功能，添加了打印功能
是一个可以向目的写入的输出流
目的：File
字符串形式的路径
字节输出流
*/
PrintStream ps = new PrintStream("tt.txt");
//一次写入一个字节
//ps.write(353);//00000000 00000000 00000001 01100001 把低8位的一个字节写入
ps.println(353);//按照数据原样儿写入，也就是数据的表现形式，内部使用了转成字符串的功能，String.valueOf()
ps.write(String.valueOf(353).getBytes());
}
}
import java.io.*;
class Demo2
{
public static void main(String[] args) throws IOException
{
/*
PrintWriter:字符打印流,字符输出流的基本功能都具备
目的：File
字符串形式的路径
字节输出流
字符数出流
*/
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
//PrintWriter pw = new PrintWriter(System.out,true);
PrintWriter pw2 = new PrintWriter(new FileWriter("t.txt"),true);
String line = null;
while((line = br.readLine())!=null)
{
if("over".equals(line))
break;
pw2.println(line);
//pw.flush();
}
}
}
//序列流:SequenceInputStream
import java.io.*;
import java.util.*;
class Demo3
{
public static void main(String[] args) throws IOException
{
FileInputStream fis1= new FileInputStream("Demo1.java");
FileInputStream fis2= new FileInputStream("Demo2.java");
FileInputStream fis3= new FileInputStream("Demo3.java");
Vector<FileInputStream> v= new Vector<FileInputStream>();
v.add(fis1);
v.add(fis2);
v.add(fis3);
Enumeration<FileInputStream> en = v.elements();
SequenceInputStream sis = new SequenceInputStream(en);
FileOutputStream fos = new FileOutputStream("hebing.java");
byte[] b = new byte[1024];
int len = 0;
while((len = sis.read(b))!=-1)
{
fos.write(b,0,len);
}
sis.close();
fos.close();
}
}
import java.io.*;
class Demo1
{
public static void main(String[] args)throws IOException
{
/*
PrintStream:打印流，具备字节输出流的基本功能，添加了打印功能
是一个可以向目的写入的输出流
目的：File
字符串形式的路径
字节输出流
*/
PrintStream ps = new PrintStream("tt.txt");
//一次写入一个字节
//ps.write(353);//00000000 00000000 00000001 01100001 把低8位的一个字节写入
ps.println(353);//按照数据原样儿写入，也就是数据的表现形式，内部使用了转成字符串的功能，String.valueOf()
ps.write(String.valueOf(353).getBytes());
}
}
import java.io.*;
class Demo2
{
public static void main(String[] args) throws IOException
{
/*
PrintWriter:字符打印流,字符输出流的基本功能都具备
目的：File
字符串形式的路径
字节输出流
字符数出流
*/
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
//PrintWriter pw = new PrintWriter(System.out,true);
PrintWriter pw2 = new PrintWriter(new FileWriter("t.txt"),true);
String line = null;
while((line = br.readLine())!=null)
{
if("over".equals(line))
break;
pw2.println(line);
//pw.flush();
}
}
}
//序列流:SequenceInputStream
import java.io.*;
import java.util.*;
class Demo3
{
public static void main(String[] args) throws IOException
{ /*
FileInputStream fis1= new FileInputStream("Demo1.java");
FileInputStream fis2= new FileInputStream("Demo2.java");
FileInputStream fis3= new FileInputStream("Demo3.java");
Vector<FileInputStream> v= new Vector<FileInputStream>();
v.add(fis1);
v.add(fis2);
v.add(fis3);
Enumeration<FileInputStream> en = v.elements();*/
ArrayList<FileInputStream> list = new ArrayList<FileInputStream>();
for(int i=1;i<=3;i++)
{
list.add(new FileInputStream("Demo"+i+".java"));
}
Enumeration<FileInputStream> en = Collections.enumeration(list);
SequenceInputStream sis = new SequenceInputStream(en);
FileOutputStream fos = new FileOutputStream("hebing2.java");
byte[] b = new byte[1024];
int len = 0;
while((len = sis.read(b))!=-1)
{
fos.write(b,0,len);
}
sis.close();
fos.close();
}
}
反射
package com.qianfeng.reflect;
public class Demo1 {
public Demo1() {
// TODO Auto-generated constructor stub
}
/**
*反射：动态获取类(class)及类中成员，并对类中的成员运行
*
*怎么获取到Class对象
*
*动态获取Person.class对象
*获取方式有三种：
*1：使用Object中的getClass()方法
* 需要先创建对象，所以的需要其所属的类实现存在
*:2：每个数据类型都有一个静态的属性class,通过该属性可以得到其所属的字节码文件对象
* 不需要创建对象了，但是需要那个类存在
* 3:Class.forName()只需要提供一个字符串，这个字符串的内容是类的名字
*
*/
public static void main(String[] args) throws ClassNotFoundException {
//getClass1();
//getClass2();
getClass3();
}
private static void getClass3() throws ClassNotFoundException {
Class claz = Class.forName("com.qianfeng.reflect.Person");
System.out.println(claz);
}
private static void getClass2() {
Class claz1 = Person.class;
Class claz2 = Person.class;
System.out.println(claz1==claz2);
}
private static void getClass1() {
Person p1 = new Person();
Class claz = p1.getClass();//Person.class
Person p2 = new Person();
Class claz2 = p2.getClass();//Person.class
System.out.println(claz==claz2);
}
}
package com.qianfeng.reflect;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
public class Demo2 {
public Demo2() {
// TODO Auto-generated constructor stub
}
/**
* 动态获取类并创建对象
* @throws ClassNotFoundException
* @throws IllegalAccessException
* @throws InstantiationException
* @throws SecurityException
* @throws NoSuchMethodException
* @throws InvocationTargetException
* @throws IllegalArgumentException
*/
public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, NoSuchMethodException, SecurityException, IllegalArgumentException, InvocationTargetException {
createObj1();
createObj2();
}
//使用带参数的构造方法创建对象
private static void createObj2() throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
//Person p = new Person("lisi",23);
Class claz = Class.forName("com.qianfeng.reflect.Person");
Constructor cons = claz.getConstructor(String.class,int.class);
Object obj = cons.newInstance("lili",23);
System.out.println(obj);
}
private static void createObj1() throws ClassNotFoundException, InstantiationException, IllegalAccessException {
//Person p = new Person();
Class claz = Class.forName("com.qianfeng.reflect.Person");//Person.class
Object obj = claz.newInstance();//用的是默认的空参数的构造方法
System.out.println(obj);
}
}
package com.qianfeng.reflect;
import java.lang.reflect.Field;
public class Demo3 {
public Demo3() {
// TODO Auto-generated constructor stub
}
/**
* 动态创建对象并给属性赋值
* @throws ClassNotFoundException
* @throws SecurityException
* @throws NoSuchFieldException
* @throws IllegalAccessException
* @throws InstantiationException
*/
public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException, SecurityException, InstantiationException, IllegalAccessException {
accessField1();
}
//动态创建对象并给属性赋值
private static void accessField1() throws ClassNotFoundException, NoSuchFieldException, SecurityException, InstantiationException, IllegalAccessException {
//Person p = new Person();
//p.name = "";
Class claz = Class.forName("com.qianfeng.reflect.Person");
//Field field = claz.getField("name");//只能获取公共的成员属性
Field field = claz.getDeclaredField("name");//只要是在类中的声明的就可以得到
//创建一个Person类型的对象
Object obj = claz.newInstance();
//设置可以访问该属性---暴力访问
field.setAccessible(true);
field.set(obj, "zhangsan");
System.out.println(obj);
}
}
package com.qianfeng.reflect;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
public class Demo4 {
public Demo4() {
// TODO Auto-generated constructor stub
}
/**
* 动态执行类中的方法
* @throws ClassNotFoundException
* @throws SecurityException
* @throws NoSuchMethodException
* @throws InvocationTargetException
* @throws IllegalArgumentException
* @throws IllegalAccessException
* @throws InstantiationException
*/
public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
invokeMethod1();
invokeMethod2();
invokeMethod3();
}
private static void invokeMethod3() throws ClassNotFoundException, NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
Class claz = Class.forName("com.qianfeng.reflect.Person");
Method m = claz.getMethod("fun",null);
m.invoke(null,null);
}
private static void invokeMethod2() throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
Class claz = Class.forName("com.qianfeng.reflect.Person");
Method m = claz.getMethod("method", String.class);
//创建对象
Object obj = claz.newInstance();
m.invoke(obj, "haha");
}
//执行无参数的方法
private static void invokeMethod1() throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
//Person p = new Person();
//p.show();
Class claz = Class.forName("com.qianfeng.reflect.Person");
//得到方法
Method m = claz.getMethod("show",null);
//创建对象
Object obj = claz.newInstance();
m.invoke(obj, null);
}
}
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