Article directory
standard input stream
package heima;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
public class P312 {
public static void main(String[] args) throws IOException {
//public static final InputStream in:标准输入流
InputStream is =System.in;
// //1.只能输入字符
// int by;
// while ((by = is.read())!=-1){
// System.out.println((char) by);
// }
// //2.把字符转换为字符流
// InputStreamReader isr = new InputStreamReader(is);
//3.实现字符流一次读取一行数据
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.println("请输入一个字符串：");
String line = br.readLine();
System.out.println("你输入的字符串是："+line);
System.out.println("请输入一个整数：");
int i = Integer.parseInt(br.readLine());
System.out.println("你输入的整数是："+i);
}
}
output:
It is too troublesome to implement by yourself, java provides a method for us to use
Scanner sc = new Scanner(System.in)
standard output stream
package heima;
import java.io.PrintStream;
public class P313 {
public static void main(String[] args) {
//pulic sattic final PrintStream out:标准输出流
PrintStream ps = System.out;
//能够方便地打印各种数据
// ps.print("hello");
// ps.print(100);
//
// ps.println("hello");
// ps.println(100);
//System.out的本质是一个字节输出流
System.out.println("hello");
System.out.println(100);
System.out.println();
// System.out.print();
}
}
Note: Direct System.out.print(); without parameters is wrong
byte print stream
Transcoding: Refers to converting to the corresponding ASCII code
package heima;
import java.io.FileNotFoundException;
import java.io.PrintStream;
public class P314 {
public static void main(String[] args) throws FileNotFoundException {
//PrintStream(String fileName)：使用指定的文件名创建新的打印流
PrintStream ps = new PrintStream("C:\\Users\\路聃\\Desktop\\Java\\ps.txt");
//写数据
//字节输出流有的方法
ps.write(97); //a
//使用特有方法写数据
ps.print(97); //97
//释放资源
ps.close();
}
}
character print stream
package heima;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
public class P315 {
public static void main(String[] args) throws IOException {
//PrintWriter(String fileName)：使用指定的文件名创建一个新的PrintWriter,而不需要自动执行行的刷新
// PrintWriter pw = new PrintWriter("C:\\Users\\路聃\\Desktop\\Java\\pw.txt");
//
// pw.write("hello");
// pw.write("\r\n");
// pw.flush();
// pw.write("world");
// pw.write("\r\n");
// pw.flush();
//
// pw.println("hello");//输出失败
// /*原因
// pw.write("hello");
// pw.write("\r\n");
// */
//PrintWriter (Writer out,boolean autoFlush)：创建一个新的PrintWriter
PrintWriter pw = new PrintWriter(new FileWriter("C:\\Users\\路聃\\Desktop\\Java\\pw.txt"),true);//true代表开启自动刷新flush()
pw.println("hello");
pw.println("world");
}
}
Case – copy java file (file print stream version)
package heima;
import java.io.*;
public class P316 {
public static void main(String[] args) throws IOException {
/*
//根据数据源创建字符输入流对象
BufferedReader br = new BufferedReader(new FileReader("C:\\IntelliJ IDEA Community Edition 2022.2.3\\study\\src\\heima\\P315.java"));
//根据目的地创建字符输出流对象
BufferedWriter bw = new BufferedWriter(new FileWriter("C:\\Users\\路聃\\Desktop\\Java\\ts.java"));
//读写数据，复制文件
String line;
while ((line=br.readLine())!=null){
bw.write(line);
bw.newLine();
bw.flush();
}
//释放资源
bw.close();
br.close();
*/
//根据数据源创建字符输入流对象
BufferedReader br = new BufferedReader(new FileReader("C:\\IntelliJ IDEA Community Edition 2022.2.3\\study\\src\\heima\\P315.java"));
//根据目的地创建字符输出流对象
PrintWriter pw = new PrintWriter(new FileWriter("C:\\Users\\路聃\\Desktop\\Java\\te.java",true));
//读写数据，复制文件
String line;
while ((line=br.readLine())!=null){
pw.println(line);
}
//释放资源
pw.close();
br.close();
}
}
object serialization stream
serialized stream
Be sure to define a marker interface Serializable in the class
package heima;
import heima.common.Student;
import java.io.*;
public class P317 {
public static void main(String[] args) throws IOException {
//ObjectOutputStream (OutputStream out)：创建一个写入指定的OutputStrem的ObjectOutputStream
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream( "C:\\Users\\路聃\\Desktop\\Java\\oos.txt"));
//创建对象
Student s = new Student("小林",30);
//void writeObject(Object obj)：将指定的对象写入ObjectOutputStream
oos.writeObject(s);
//释放资源
oos.close();
}
}
deserialize stream
output the sequence flow above
package heima;
import heima.common.Student;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
public class P318 {
public static void main(String[] args) throws IOException, ClassNotFoundException {
//ObjectInputStream(InputStream in)：创建从指定的InputStream读取的ObjectInputStream
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("C:\\Users\\路聃\\Desktop\\Java\\oos.txt"));
//Objext readObject()：从ObjectInputStream读取一个对象
Object obj = ois.readObject();
Student s = (Student) obj;
System.out.println(s.getName()+","+s.getAge());
ois.close();
}
}
serialVersionID&transient
package heima;
import heima.common.Student;
import java.io.*;
public class P319 {
public static void main(String[] args) throws IOException, ClassNotFoundException {
write();
// read();
}
//序列化
private static void write() throws IOException {
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("C:\\Users\\路聃\\Desktop\\Java\\oos.txt"));
Student s = new Student("小林",30);
oos.writeObject(s);
oos.close();
}
//反序列化
private static void read() throws IOException, ClassNotFoundException {
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("C:\\Users\\路聃\\Desktop\\Java\\oos.txt"));
Object obj = ois.readObject();
Student s = (Student) obj;
System.out.println(s.getName()+","+s.getAge());
ois.close();
}
}
For the above code, if the content of the Student class is changed after the execution of read(), and then write() is executed, an error will be reported.
reason
The following changes need to be made to Student:
The use of Properties as a Map collection
package heima;
import java.util.Objects;
import java.util.Properties;
import java.util.Set;
public class P320 {
public static void main(String[] args) {
//创建集合对象
//1.err --想当然的把Properties当作泛型
// Properties<String,String> prop = new Properties<String,String>();
Properties prop = new Properties();
//存储元素
prop.put("item01","小林");
prop.put("item02","小王");
prop.put("item03","小雨");
//遍历集合
Set<Object> keySet = prop.keySet();
for (Object key : keySet){
Object value = prop.get(key);
System.out.println(key+","+value);
}
}
}
Properties as unique methods of collections
package heima;
import java.util.Properties;
import java.util.Set;
public class P321 {
public static void main(String[] args) {
//创建集合对象
Properties prop = new Properties();
//Object setProperty(String key,String value)：设置集合的键和值，都是String类型，底层调用Hashtable方法put
prop.setProperty("item01","小林");
/* 方法来源
Object setProperty(String key,String value){
return put(key,value);
}
Object put(Object key,Object value){
return map.put(key,value);
}
设计：把一个接受Object对象的方法，改为只能接受String对象，设计巧妙
*/
prop.setProperty("item02","小张");
prop.setProperty("item03","小文");
//String getProperty(String key)：使用此属性列表中指定的键搜索属性
System.out.println(prop.getProperty("item01"));
System.out.println(prop);
//Set<String> stringPropertyNames()：从该属性列表中返回一个不可修改的键集，其中键及其对应的值是字符串
Set<String> names = prop.stringPropertyNames();
for (String key : names){
// System.out.println(key);//输出所以的键名
String value = prop.getProperty(key);
System.out.println(key+","+value);//输出键和对应的值
}
}
}
The method of combining Properties with IO stream
package heima;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Properties;
public class P322 {
public static void main(String[] args) throws IOException {
//把集合中的数据保存到文件
// myStore();
//把文件中的数据加载到集合
myLoad();
}
private static void myLoad() throws IOException, IOException {
Properties prop = new Properties();
//void load(Reader reader)：
FileReader fr = new FileReader("C:\\Users\\路聃\\Desktop\\Java\\fw.txt");
prop.load(fr);
fr.close();
System.out.println(prop);
}
private static void myStore() throws IOException {
Properties prop = new Properties();
prop.setProperty("item01","小林");
prop.setProperty("item02","小王");
prop.setProperty("item03","小黄");
//void store(Writer writer,String comments)：
FileWriter fw = new FileWriter("C:\\Users\\路聃\\Desktop\\Java\\fw.txt");
prop.store(fw,null);
fw.close();
}
}
output:
Execute only myStore() first, then only myLoad()
Case – Number of games
package heima;
import heima.common.GuessNumber;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Properties;
public class P323 {
public static void main(String[] args) throws IOException {
//从文件中读取数据到Properties集合,用load()方法实现
Properties prop = new Properties();
FileReader fr = new FileReader("C:\\Users\\路聃\\Desktop\\Java\\game.txt");
prop.load(fr);
fr.close();
//通过Properties集合获取到玩游戏的次数
String count = prop.getProperty("count");
int number = Integer.parseInt(count);
//判断次数是否到达3次了
if (number >= 3){
//如果到了
System.out.println("游戏试玩已结束，想玩请充值(www.itcast.cn)");
}else {
//继续玩游戏
GuessNumber.start();
//次数+1，重新写回文件，用Properties的store()方法实现
number++;
//String.valueOf()：转换位字符串
prop.setProperty("count",String.valueOf(number));
FileWriter fw = new FileWriter("C:\\Users\\路聃\\Desktop\\Java\\game.txt");
prop.store(fw,null);
fw.close();
}
}
}
//1 load
//2 store
GuessNumber.java
package heima.common;
import java.util.Random;
import java.util.Scanner;
public class GuessNumber {
private GuessNumber(){
}
public static void start(){
//要完成猜数字的游戏，首先要有一个要猜的数字，使用随机数生成该数字，范围1到200
Random r = new Random();
int number = r.nextInt(100)+1;
while (true){
Scanner sc = new Scanner(System.in);
System.out.println("请输入你要猜的数字：");
int guessNumber = sc.nextInt();
//比较输入的数字喝系统产生的数据
if (guessNumber > number){
System.out.println("你猜的的数字"+guessNumber+"大了");
}else if (guessNumber <number){
System.out.println("你猜的数字"+guessNumber+"小了");
}else {
System.out.println("恭喜你猜中了");
break;
}
}
}
}