返回ArrayList给出错误:找不到符号

Question

我试图返回一个ArrayList,但在最后我得到错误:找不到符号.我在列表中添加了一些字符串和双打并将其返回到所谓的字符串.

错误:

./Sample.java:55: error: cannot find symbol
        return placeMatch;
               ^
  symbol:   variable placeMatch
  location: class Sample
1 error

考虑到提到的关于try catch的内容我将我的声明声明移到了顶部,我得到:

./Sample.java:54:错误:不兼容的类型返回placeMatch; ^ required:找到的字符串:ArrayList

实际代码:

import java.util.ArrayList;
//...other imports

public class Sample
  extends UnicastRemoteObject
  implements SampleInterface {



    public Sample() throws RemoteException {

    }

    public String invert(String city, String state) throws RemoteException {
        try{


 ArrayList<Object> placeMatch = new ArrayList<Object>();
        // Read the existing address book.
        PlaceList place =
        PlaceList.parseFrom(new FileInputStream("places-proto.bin"));

        // Iterates though all people in the AddressBook and prints info about them.

        for (Place Placeplace: place.getPlaceList()) {
        //System.out.println("STATE: " + Placeplace.getState());
            if(Placeplace.getName().startsWith(city)){
                placeMatch.add(Placeplace.getName());
                placeMatch.add(Placeplace.getState());
                placeMatch.add(Placeplace.getLat());
                placeMatch.add(Placeplace.getLon());
                break;
            }


          }

        }catch(Exception e){
               System.out.println("opening .bin failed:" + e.getMessage());
        }
        return placeMatch;
    }

}

Answer 1

你需要声明:

ArrayList<Object> placeMatch = new ArrayList<Object>();

在try块之外.

第二个问题:

方法返回类型是String.你不能回来ArrayList<Object>.

解决方案取决于您需要做什么.您可以更改返回类型:

public List<Object> invert(String city, String state) throws RemoteException {