java 中File类的exists()方法

发布网友发布时间：2022-05-14 10:16

共3个回答

热心网友时间：2023-09-18 00:09

就是如果存在的话返回“true”，否则就是返回“false”。举例：
//判断文件是否存在
public static String fileExists(String plainFilePath){
File file=new File(plainFilePath);
if(!file.exists()) {
return "false";
} else{

return "true";
}
}

热心网友时间：2023-09-18 00:10

file 只能操作本地文件
用URL类以及httpurlconnection可以判断追问给点思路指教一下

追答import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;

import ch.unifr.article.util.Constant;

public class ReadInformation {

/**
* @param args
*/
private InputStream l_urlStream;

private FileWriter fw;

private String coding = "UTF-8";

public String getUrlText(String s) {
String text = "";
String sCurrentLine = "";
try {
URL url = new URL(s);
java.net.HttpURLConnection l_connection = (java.net.HttpURLConnection) url
.openConnection();
l_connection.connect();
l_urlStream = l_connection.getInputStream();
java.io.InputStreamReader read = new InputStreamReader(l_urlStream,
coding);
java.io.BufferedReader l_reader = new java.io.BufferedReader(read);

while ((sCurrentLine = l_reader.readLine()) != null) {
text += sCurrentLine;
}// viewSource(url);
} catch (MalformedURLException ex) {
System.out.println("网络连接错误:" + s);
ex.printStackTrace();
} catch (FileNotFoundException e) {
System.out.println("文件不存在:" + s);
e.printStackTrace();

} catch (IOException e) {
System.out.println("其他IO错误:" + s);
e.printStackTrace();
}
return text;
}

public static void main(String[] args) {
ReadInformation ri = new ReadInformation();
String url = "http://xxxx.com/sss.txt";//此处请lz填写txt地址
System.out.println(ri.getUrlText(url));
}

}

热心网友时间：2023-09-18 00:10

这个貌似file类不行，
你可以用net包下面的url跟httpurlconnection这两个类看看