java怎么读取数据

java怎么读取数据

1、从控制台读取数据

使用Scanner类来读取控制台的输入（推荐教程：java教程）

public static void main(String[] args) {    Scanner in = new Scanner(System.in);  String a = in.nextLine();  System.out.println(a);}

2、从本地读取文件

使用FileInputStream、InputStreamReader、BufferedReader类读取本地数据

 public void readTxtFile(String filePath) {        try {            File file = new File(filePath);            if (file.isFile() && file.exists()) {                InputStreamReader isr = new InputStreamReader(new FileInputStream(file), "utf-8");                BufferedReader br = new BufferedReader(isr);                String lineTxt = null;                while ((lineTxt = br.readLine()) != null) {                    System.out.println(lineTxt);                }                br.close();            } else {                System.out.println("文件不存在!");            }        } catch (Exception e) {            System.out.println("文件读取错误!");        }    }

3、从网络读取文件

使用URLConnection 、InputStreamReader、BufferedReader读取网络数据。

public class Main {    public static void main(String[] args) {    String url = "http://www.php.cn/test.txt";    String result = "";    BufferedReader in = null;    try {        //生成URL        URL realUrl = new URL(url);        //初始化连接到特定URL的连接通道        URLConnection connection = realUrl.openConnection();        //开始实际连接        connection.connect();        //数据读取        in = new BufferedReader(new InputStreamReader(connection.getInputStream()));                //临时存储一行数据        String line;        while((line = in.readLine()) != null) {            result += line;        }    } catch (Exception e) {        e.printStackTrace();    } finally {        try {            if (in != null) {                in.close();            }        } catch (Exception e2) {            e2.printStackTrace();        }    }    System.out.println(result);  }}