java - 这个 Java HashMap 声明有什么问题？轻松点

Question

private HashMap<String, IMapper> mapper = new HashMap<String, IMapper>();

看起来很无辜，但 Eclipse 却在提示所有事情中的分号。

Eclipse 错误:标记“;”的语法错误，无效的 AssignmentOperator

谢谢

全类:

package persistence;

import java.util.UUID;
import java.util.HashMap;

import domain.Task;

public class PersistanceFacade {

    private static PersistanceFacade uniqueInstance = null;
    private HashMap<String, IMapper> mapper = new HashMap<String, IMapper>();


    (SingleTaskRDBMapper) mapper.put("SingleTask", new SingleTaskRDBMapper());

    public PersistanceFacade() {};

    public static synchronized PersistanceFacade getUniqueInstance() {
        if (uniqueInstance == null) {
            uniqueInstance = new PersistanceFacade();
            return uniqueInstance;
        }
        else return uniqueInstance;
    }

    @SuppressWarnings("unchecked")
    public Object get(UUID oid, Class type) {
        Object mappers;
        IMapper mapper = ((HashMap<String, IMapper>) mappers).get(type);
    }

}

Answer 1

线

(SingleTaskRDBMapper) mapper.put("SingleTask", new SingleTaskRDBMapper());

不合时宜。你应该把它放在构造函数中:

public PersistanceFacade() {
  mapper.put("SingleTask", new SingleTaskRDBMapper());
}

另请注意，我在构造函数的右大括号后删除了多余的分号。我也不确定 get 方法中发生了什么。您声明对象 mappers 但从未对其进行初始化。那肯定会导致错误。