FileReader和FileWriter的使用实例

package io;

import org.junit.Test;

import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Map;
import java.util.Properties;

public class IoDemoTest {
    private FileReader fr = null;
    private FileWriter fw = null;
    private File file = null;

    @Test
    public void fun() {
        try {
            FileReader fr = new FileReader(new File(IoDemoTest.class.getResource("/a.txt").getPath()));
            int i = 0;
            /*System.out.println(1 / 0);*/
            while ((i = fr.read()) != -1) {
                System.out.print((char) i);
            }

            fr.close();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            System.out.println();
            System.out.println("无论什么情况都会被执行");
        }
    }

    @Test
    public void write() {
        /*Map<String, String> getenv = System.getenv();
        for(Map.Entry<String,String> en :getenv.entrySet()){
            System.out.println("key值是" + en.getKey());
            System.out.println("value值是" + en.getValue());
        }*/

        /*String pwd = System.getenv("PWD");
        System.out.println(pwd);*/

        String getdir = System.getProperty("user.dir");
        /*System.out.println(getdir);*/

        File file = new File(getdir + "/src/main/resources/b.txt");
        if (!file.exists()) {
            try {
                file.createNewFile();
            } catch (IOException e) {
                e.printStackTrace();
            }
        } else {
            try {
                FileWriter fw = new FileWriter(file);
                fw.write("io写数据");
                fw.flush();
                /*fw.close();*/
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    @Test
    public void copy0() throws Exception {
        fr = new FileReader("C:\Users\15082157\Desktop\自我介绍.txt");
        /*int i = 0;
        while ((i = fr.read()) != -1) {
            System.out.print((char) i);
        }*/

        String getdir = System.getProperty("user.dir");
        file = new File(getdir + "/src/main/resources/copy0.txt");
        if (!file.exists()) {
            file.createNewFile();
            /*FileWriter fw = new FileWriter(file);
            while ((i = fr.read()) != -1) {
                fw.write((char) i);
            }
            fw.flush();
            fr.close();
            fw.close();*/
            characterCopy();
            System.out.println("新创建文件，再copy字符");
        } else {
            /*FileWriter fw = new FileWriter(file);
            while ((i = fr.read()) != -1) {
                fw.write((char) i);
            }
            fw.flush();
            fr.close();
            fw.close();*/
            characterCopy();
            System.out.println("已有文件，直接copy字符");
        }

    }

    public void characterCopy() throws Exception {
        int i = 0;
        fw = new FileWriter(file);
        long beginTime = getCurrentTime1();
        while ((i = fr.read()) != -1) {
            fw.write((char) i);
        }
        fw.flush();
        long endTime = getCurrentTime1();
        float time = (endTime - beginTime) / 1000F;
        System.out.println("copy时间为" + time + "s");
        fr.close();
        fw.close();

    }

    @Test
    public void getCurrentTime(){
        SimpleDateFormat df= new SimpleDateFormat("yyyy-MM-dd HH:mm:ssSSS");
        /*System.out.println(df);*/
        System.out.println(df.format(new Date()));
    }


    public long getCurrentTime1(){
        long currentTime= System.currentTimeMillis();
        System.out.println(currentTime);
        return currentTime;
    }
}

windows获取工程当前路径使用这个方法  System.getProperty("user.dir");