Question

大家好，我对此代码有疑问：

//Class FileManip
public class FileManip{

private HTTPRequest<List<String>> addMe = new HTTPRequest<List<String>>();

    public void openFile(){

            try{
                BufferedReader buff = new BufferedReader(new FileReader("Saturday.txt"));
                try{
                    Double ctr = 0.0;
                    String readHTTPURIFromTxt = buff.readLine();
                    while (readHTTPURIFromTxt!=null){

                        if (!readHTTPURIFromTxt.isEmpty()){
                            addMe.putListHTTPCharTable(parseHTTPReqToCharbyChar(readHTTPURIFromTxt), ctr);
                            ctr++;
                        }
                    readHTTPURIFromTxt = buff.readLine();
                    }
                }

                finally{
                    buff.close();
                }   

            }
            catch(FileNotFoundException e){
                System.out.println("File not found"+e);
            }
            catch(IOException e){
                System.out.println("oist exception");
            }
        }

    public List<String> parseHTTPReqToCharbyChar(String getHTTP){ 
            List<String> parsingReq = new ArrayList<String>();
            String convChar=null;

                for (int x = 0; x<getHTTP.length(); x++){
                    convChar = Character.toString(getHTTP.charAt(x));
                    parsingReq.add(convChar);
                }

            return parsingReq;
        }
}


    //Class HTTPRequest
    public class HTTPRequest<T> {

    private LinkedHashMap<List<T>, Double> tableOfInitProbList = new LinkedHashMap<List<T>, Double>();

    public HTTPRequest(){
        }

    public HTTPRequest(List<T> entry, Double value){
            tableOfInitProbList.put(entry, value);
        }

    public void putListHTTPCharTable(List<T> uri, Double value){
            tableOfInitProbList.put(uri, value);
        }

    }

问题在于

行

addMe.putListHTTPCharTable(parseHTTPReqToCharbyChar(readHTTPURIFromTxt), ctr);

在if语句中的类filemanip openfile方法。我写了putListHttpCharTable来取2个参数List＆lt; T>和Double但每当我传递参数parseHTTPReqToCharbyChar（readHTTPURIFromTxt）时返回类型为List，就会出现编译时错误。它读取

方法putListHTTPCharTable（List＆gt;，Double）类型为HTTPRequest＆gt;不适用于参数（List，Double）

我传递了一个List＆lt;字符串＆gt;返回类型，但不知何故编译器正试图将其读作List＆lt;列表＆lt; T> ＆GT;或列表＆lt;列表＆lt;字符串＆gt; ＆GT;而不仅仅是List＆lt;字符串＆gt;。无论如何要解决这个问题吗？

Answer 1

因为：

HTTPRequest<List<String>>

表示：

T <=> List<String>

所以编译器会看到这个（对于你的＆＃34; addMe＆＃34;变量）：

//Class HTTPRequest
    public class HTTPRequest<List<String>> {

    private LinkedHashMap<List<List<String>>, Double> tableOfInitProbList = new LinkedHashMap<List<List<String>>, Double>();

    public HTTPRequest(){
        }

    public HTTPRequest(List<List<String>> entry, Double value){
            tableOfInitProbList.put(entry, value);
        }

    public void putListHTTPCharTable(List<List<String>> uri, Double value){
            tableOfInitProbList.put(uri, value);
        }

    }

Answer 2

您将T设为List<String>

然后该方法正在寻找List<T>，因此您最终得到List<List<String>>

如果您将班级更改为：

，这应该有效

public class HTTPRequest<T> {

    private LinkedHashMap<T, Double> tableOfInitProbList = new LinkedHashMap<List<T>, Double>();

    public HTTPRequest(){
        }

    public HTTPRequest(T entry, Double value){
            tableOfInitProbList.put(entry, value);
        }

    public void putListHTTPCharTable(T uri, Double value){
            tableOfInitProbList.put(uri, value);
        }

}

或者，如果您只想使用泛型参数指定列表类型，则此声明应该起作用：

private HTTPRequest<String> addMe = new HTTPRequest<String>();

在java generics参数List <t> </t>中需要帮助

2 个答案: