Question

我正在尝试打印网站的HTML页面源。我在第45行将String初始化为null。但是，当我尝试打印新附加的字符串时，将显示null关键字。

我尝试删除String的初始化。

 public class MainActivity extends AppCompatActivity {
  public class ToPrintWebSiteSource extends AsyncTask<String,Void,String>{
    @Override
        HttpURLConnection httpURLConnection = null;
        String result = null;
        try {
            siteUrl = new URL(urls[0]);
            httpURLConnection = (HttpURLConnection) siteUrl.openConnection();
            InputStream in = httpURLConnection.getInputStream();
            InputStreamReader reader = new InputStreamReader(in);
            int data = reader.read();
            while(data!= -1){
                char character = (char) data;
                result += character;
                data = reader.read();
            }
        }
        catch (Exception e) {
            Log.i("Error:","The code is not working....");
            e.printStackTrace();
        }
        return  result;

    }
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    String result = null;
    ToPrintWebSiteSource helloWorld = new ToPrintWebSiteSource();
    try {
        result = helloWorld.execute("https://web.ics.purdue.edu/~gchopra/class/public/pages/webdesign/05_simple.html").get();
    } catch (ExecutionException e) {
        e.printStackTrace();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    Log.i("Page Source Html:", result);
    }
   }

我收到的结果是：

null<html>

<head>
<title>A very simple webpage</title>
<basefont size=4>
</head>

Answer 1

您应该将其设置为空字符串，而不是null。当您用null连接字符串时，字符串“ null”被添加到其中，而不是为空。

更好的是，您甚至不应该在这里使用字符串连接。这就是StringBuilder的作用。

    HttpURLConnection httpURLConnection = null;
    StringBuilder result = new StringBuilder();
    char buffer[] = new char[100];

    try {
        siteUrl = new URL(urls[0]);
        httpURLConnection = (HttpURLConnection) siteUrl.openConnection();
        InputStream in = httpURLConnection.getInputStream();
        InputStreamReader reader = new InputStreamReader(in);

        for (int n; (n = reader.read(buffer)) != -1;) {
            result.append(buffer, 0, n);
        }
    }
    catch (Exception e) {
        Log.i("Error:","The code is not working....");
        e.printStackTrace();
    }
    return result.toString();

这一次将多个字符读取到一个char数组中，将字符追加到StringBuilder上，直到读取所有数据为止。将数组的大小设置为100是任意的，如果您想一次读取更多数据，则可以使其更大。

将字符附加到字符串后，如何删除“空”字？

1 个答案: