环境变量,属性文件,文件基础操作,目录基础操作,遍历指定后缀名文件

import java.util.Enumeration;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Properties;

public class Environment {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Map<String, String> env = System.getenv();
        for (Entry<String, String> entry : env.entrySet()) {//jdk1.5 环境变量
            System.out.println("key: "+entry.getKey());
            System.out.println("value: "+entry.getValue());
        }
        String s=System.getenv("JAVA_HOME");
        System.out.println("JAVA_HOME的环境变量是:"+s);
        
        Properties properties=System.getProperties();//得到属性
        for (Entry<Object,Object> objectEntry : properties.entrySet()) {
            System.out.println("key: "+objectEntry.getKey());
            System.out.println("value: "+objectEntry.getValue());
        }
        
        String p=System.getProperty("java.version");
        System.out.println("java版本:  "+p);
        
        //设置系统属性
        setProperty("manu", "sas");
        System.out.println(properties.getProperty("manu"));
         
        //列出全部系统属性名
        Enumeration<String> names=(Enumeration<String>) properties.propertyNames();
        while (names.hasMoreElements()) {
            String sall = (String) names.nextElement();
            System.out.println(sall);
        }
    }
    
    private static void setProperty(String key,String value) {
        Properties properties=System.getProperties();
        properties.setProperty(key, value);
    }

}

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Properties;

public class propertyfile {
    public static void main(String[] args) throws FileNotFoundException,
            IOException {
        Properties properties = new Properties();
    
        File inputfile = new File("config.properties");
        // 文件内容放入hashmap
        properties.load(new FileInputStream(inputfile));
        System.out.println(properties.getProperty("manu"));
        
        //内存中
        properties.setProperty("i11440", "i11111");
        //文件定位 目录可变 相对路径 根目录开始的
        File outputfile = new File("config/out.properties");
        //读取 新建properties文件 写入数据
        properties.store(new FileOutputStream(outputfile), "properties的备注");
    }
}

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.InvalidPropertiesFormatException;
import java.util.Properties;

public class propertyxml {
    public static void main(String[] args)
            throws InvalidPropertiesFormatException, FileNotFoundException,
            IOException {
        Properties properties = new Properties();
        File file = new File("config.xml");
        properties.loadFromXML(new FileInputStream(file));
        // String s=properties.getProperty("admin_username");
        // System.out.println(s);
        properties.setProperty("key", "value");
        File out = new File("new.xml");
        properties.storeToXML(new FileOutputStream(out), "备注");
    }
}

import java.awt.peer.SystemTrayPeer;
import java.io.File;
import java.io.IOException;

public class fileDemo {

    public static void main(String[] args) throws Exception {
        // 基础文件操作
        
         File file = new File("config.properties");
         System.out.println("文件名字:  "+file.getName());
         System.out.println("绝对路径:  "+file.getAbsolutePath());
         System.err.println("是否存在: "+file.exists());
         System.out.println("相对路径: "+file.getParent());
         System.out.println("当前系统的文件分隔符:  "+File.separator);
         System.out.println("系统属性中得到系统文件分隔符: "+System.getProperty("file.separator"));

         File file2 = new File("src/fileIO/fileDemo. java");
         if (file2.isFile()) {
         System.out.println(file2 + "是个文件！");
         }
         //createNewFile("newfile.xml");
         //deleteFile("newfile.xml");
    }

    private static void createNewFile(String filename) throws IOException {
        File file = new File(filename);
        if (!file.exists()) {
            // createNewFile创建文件
            if (file.createNewFile()) {
                System.out.println("创建成功!");
            } else {
                System.out.println("创建不成功!");
            }
        } else {
            System.out.println("文件已经存在了！");
        }
    }

    private static void deleteFile(String filename) {
        File file = new File(filename);
        if (file.exists()) {
            //delete删除文件
            if (file.delete()) {
                System.out.println("刪除成功");
            } else {
                System.out.println("刪除不成功");
            }
        } else {
            System.out.println("文件已經刪除");
        }
    }

}

import java.io.File;
import java.io.IOException;

public class DirectoryDemo {
    // 目录基本操作
    public static void main(String[] args) throws Exception {
        // 目录位置
         File dir = new File("src/fileIO");
        
        if (dir.isDirectory()) {
            System.out.println(dir + " 是个目录啊！");
        }
        
         //目录下文件列表 不会递归下一层目录
         for (String s : dir.list()) {
         System.out.println(s);
         }
        // createSingleDir("newdir");
        // deleteSingleDir("newdir");
        // createMultiDir("test1/test2");
        // deleteMultiDir("test1/55");
        //createFileWithDir("test55/a.txt");
    }

    // 创建单一目录
    private static void createSingleDir(String sdir) {
        File dir = new File(sdir);
        if (dir.exists()) {
            return;
        }
        // 创建目录
        if (dir.mkdir()) {
            System.out.println("create ok");
        } else {
            System.out.println("create !ok");
        }
    }

    // //删除单一目录
    private static void deleteSingleDir(String sdir) {
        File dir = new File(sdir);
        if (dir.exists()) {
            // 目录删除
            if (dir.delete()) {
                System.out.println("delete ok");
            } else {
                System.out.println("delete !ok");
            }
        } else {
            System.out.println("dir inexistence");
        }
    }

    // // 创建多个目录 目录树
    private static void createMultiDir(String sdir) {
        File dir = new File(sdir);
        if (dir.exists()) {
            return;
        }
        // 创建多个目录
        if (dir.mkdirs()) {
            System.out.println("create ok");
        } else {
            System.out.println("create !ok");
        }
    }

    // 删除目录树
    private static void deleteMultiDir(String sdir) {
        File dir = new File(sdir);
        if (dir.exists()) {
            // 多个目录删除
            if (delete(dir)) {
                System.out.println("delete ok");
            } else {
                System.out.println("delete !ok");
            }
        } else {
            System.out.println("dir inexistence");
            return;
        }
    }

    //删除目录和文件
    private static boolean delete(File dir) {
        boolean flag = true;
        if (dir.isDirectory()) {
            for (File file : dir.listFiles()) {
                // 递归删除
                flag = flag && delete(file);
            }
        }
        return flag && dir.delete();
    }
    
    //创建文件同时创建目录
    private static void createFileWithDir(String sdir) throws Exception {
        File file=new File(sdir);
        if (file.exists()) {
            return;
        }
        File dir=file.getParentFile();
        if (!dir.exists()) {
            dir.mkdirs();
        }
        file.createNewFile();
    }
    
}

import java.io.File;
import java.io.FilenameFilter;
import java.util.Scanner;

public class FilenameFilterDemo {
    // 过滤制定后缀名的文件
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner sc = new Scanner(System.in);
        System.out.println("输入目录:");
        String path = sc.nextLine();
        System.out.println("输入后缀名");
        final String suffix = sc.nextLine();
        File file = new File(path);
        // 匿名内部类 filenamefilter是接口
        String[] files = file.list(new FilenameFilter() {
            // 目录dir 文件名name
            public boolean accept(File dir, String name) {
                if (name.endsWith(suffix)) {
                    // true代表之间存入String[]
                    return true;
                }
                return false;
            }
        });

        for (String s : files) {
            System.out.println(s);
        }
    }

}