runtime可实现调用系统命令打开网页

package day;import java.io.IOException;public class Runt {    public static void main(String[] args) {        Runtime run = Runtime.getRuntime();        System.out.println("jvm最大内存量为"+ run.maxMemory());        try {            run.exec("cmd /c start http://www.baidu.com");    //打开百度        } catch (IOException e) {            e.printStackTrace();        }    }}

实现数据库的定时备份（利用多线程）

package day;import java.io.File;import java.io.IOException;import java.text.SimpleDateFormat;import java.util.ArrayList;import java.util.Collections;import java.util.Date;public class Db implements Runnable {    private int m = 0;    public Db(int m) {        this.m = m;    }    public Db() {        this.m = 5;    }    @Override    public void run() {        long ftime = 0;        int num = 0;        long start = 0;        while (true) {            start += 5;            SimpleDateFormat sd = new SimpleDateFormat("yyyHHddHHmmss");            Date d = new Date();            String ff = sd.format(d) + ".sql";            Runtime run = Runtime.getRuntime();            try {                if (start >= (this.m * 60)) {                       //m分钟后开始备份                    run.exec("cmd /c D:\\m8\\mysql-8.0.12\\bin\\mysqldump.exe -uroot -proot zzz zzz > c:\\dbtext\\" + ff);     //使用runtime实现数据库备份zzz数组库                    start = 0;                    num++;                    while (num > 3) {                               //文件夹中只存放最近三次的备份，多余则删除                        File[] f = new File("c:/dbtext").listFiles();                        var arr = new ArrayList
     
      ();                        for (File fl : f) {                            ftime = fl.lastModified();                            arr.add(ftime);                        }                        long min = Collections.min(arr);                        for (File fl : f) {                            if (fl.lastModified() == min) {                                fl.delete();                            }                        }                        num--;                    }                }            } catch (IOException e) {                e.printStackTrace();            }            try {                Thread.sleep(5000);            } catch (InterruptedException e) {                e.printStackTrace();            }        }    }}-----------------------------------------------------------------------------package day;public class Dbtext {    public static void main(String[] args) {        Db d = new Db(1);        Thread th = new Thread(d);                                            //开启线程一直执行        th.start();    }}