Question

我已经编写了一个java代码来打印我的输出文件，该文件位于文档中，但是在执行代码文件后仍然是空的。有人犯了我的错误。我正在使用netbeans来创建这个程序

码

import java.net.HttpURLConnection;
import java.net.URL;
import java.lang.*;
import java.io.*;

public class NewClass1 {

    static long start = 0;
    static long finish = 0;
    static long time;

    public static void main(String[] args) throws Exception {

        BufferedWriter bw = null;
        FileWriter fw = null;
        for (int i = 0; i <= 5; i++) {

            String stack_url = "https://www.google.lk/";

            try {
                URL url = new URL(stack_url);
                HttpURLConnection httpUrlConnect = (HttpURLConnection) url.openConnection();
                httpUrlConnect.setConnectTimeout(10);
                start = System.currentTimeMillis();
                httpUrlConnect.connect();

                if (httpUrlConnect.getResponseCode() == 200) {
                    finish = System.currentTimeMillis();
                    System.out.println(stack_url + " - " + httpUrlConnect.getResponseMessage() + " took " + (finish - start) + " Milli Seconds.");
                }

                if (httpUrlConnect.getResponseCode() == httpUrlConnect.HTTP_NOT_FOUND) {
                    System.out.println(stack_url + " - " + httpUrlConnect.getResponseMessage() + " - " + httpUrlConnect.HTTP_NOT_FOUND);
                }
            } catch (Exception e) {

            }

            time = finish - start;
            finish = System.currentTimeMillis();
            System.out.println("Total Time for page load - " + (finish - start));

            try {

                Integer _time = (int) (long) time;
                String content = Integer.toString(_time);
                fw = new FileWriter("time.sql");
                bw = new BufferedWriter(fw);
                bw.write(content);

                System.out.println("Done");

            } catch (IOException e) {

                e.printStackTrace();

            } finally {

                try {

                    if (bw != null) {
                        bw.close();
                    }

                    if (fw != null) {
                        fw.close();
                    }

                } catch (IOException ex) {

                    ex.printStackTrace();

                }
            }
        }

        Thread.sleep(1000);
    }
}

Answer 1

第一件事：

你的程序没有花费全部时间来执行，所以你必须增加时间：

httpUrlConnect.setConnectTimeout(1000);
//--------------------------------^^

第二件事：

不要在代码中创建文件，只需在之前创建它，这样就不得不将这两行移到循环之外：

fw = new FileWriter("time.sql");
bw = new BufferedWriter(fw);

第三件事：

不要在每次迭代中关闭文件，在完成后关闭文件，因此必须在循环后删除finally块并关闭文件。

bw.close();
fw.close();

您的代码应如下所示：

由用户1516873编辑

@Test
public void test44325932() {

    final String stackUrl = "https://www.google.lk/";

    // BufferedWriter is closable, it will close automatically (and close underline stream) in finally block
    try (BufferedWriter bw = new BufferedWriter(new FileWriter("time.sql"))) {

        for (int i = 0; i <= 5; i++) {
            String responseStatus;
            long start = System.currentTimeMillis();
            long finish;
            try {
                URL url = new URL(stackUrl);
                HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                connection.setConnectTimeout(5000); // 5 sec connect timeout
                connection.connect();
                if (connection.getResponseCode() == HttpURLConnection.HTTP_OK) {
                    responseStatus = "OK";
                } else { // any non 200 status counts as error
                    responseStatus = connection.getResponseCode() + " : " + connection.getResponseMessage();
                }
                // full time should be calculated after completely reading response, not after get status code, but it is depends of requirements
                // I put it here as example
                // IOUtils.readFully(connection.getInputStream(), new byte[1024]);
                connection.disconnect();
            } catch (IOException e) {                   
                responseStatus = "Exception : " + e.getClass().getSimpleName();
            } finally {
                finish = System.currentTimeMillis();
            }

            long time = finish - start;
            System.out.println("Server response: " + time + " ms, status: " + responseStatus);
            bw.write(String.valueOf(time)); // i think you should write status here, too.
            bw.newLine();
            Thread.sleep(1000);
        }
        System.out.println("Done");
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

Answer 2

您应该使用try-with-resource，如：

try (FileWriter fw = new FileWriter("D:\\time.sql"))

作为main方法的第一行，最后阻止你，你可以删除fw.close() 调用

如果您愿意，可以直接使用fw.write(content);而不是缓冲的作家。

如果您使用try with resource：

，您可以删除以下代码（因为您正在循环并且每次构造一个不需要的新对象时）：

fw = new FileWriter("time.sql");
bw = new BufferedWriter(fw);
bw.write(content);

而是使用：

fw.write(content);

我确实做了以上更改，它对我有用。

HTH， AJ

如何使用java输出到文件？

2 个答案: