正確使用泛型

Question

的從primefaces我..

public abstract class LazyDataModel<T> extends DataModel<T> implements SelectableDataModel<T>, Serializable { 

------------編輯-------------

從primefaces滿級的

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* Copyright 2009-2012 Prime Teknoloji. 
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* Licensed under the Apache License, Version 2.0 (the "License"); 
* you may not use this file except in compliance with the License. 
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* 
* http://www.apache.org/licenses/LICENSE-2.0 
* 
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package org.primefaces.model; 

import java.io.Serializable; 
import java.util.List; 
import java.util.Map; 

import javax.faces.model.DataModel; 

/** 
* Custom lazy loading DataModel to deal with huge datasets 
*/ 
public abstract class LazyDataModel<T> extends DataModel<T> implements SelectableDataModel<T>, Serializable { 

    private int rowIndex = -1; 

    private int rowCount; 

    private int pageSize; 

    private List<T> data; 

    public LazyDataModel() { 
     super(); 
    } 

    public boolean isRowAvailable() { 
     if(data == null) { 
      return false; 
     } 

     return rowIndex >= 0 && rowIndex < data.size(); 
    } 

    public int getRowCount() { 
     return rowCount; 
    } 

    public T getRowData() { 
     return data.get(rowIndex); 
    } 

    public int getRowIndex() { 
     return this.rowIndex; 
    } 

    public void setRowIndex(int rowIndex) { 
     this.rowIndex = rowIndex == -1 ? rowIndex : (rowIndex % pageSize); 
    } 

    public Object getWrappedData() { 
     return data; 
    } 
    public void setWrappedData(Object list) { 
     this.data = (List) list; 
    } 

    public int getPageSize() { 
     return pageSize; 
    } 
    public void setPageSize(int pageSize) { 
     this.pageSize = pageSize; 
    } 

    public void setRowCount(int rowCount) { 
     this.rowCount = rowCount; 
    } 

    public List<T> load(int first, int pageSize, String sortField, SortOrder sortOrder, Map<String,String> filters) { 
     throw new UnsupportedOperationException("Lazy loading is not implemented."); 
    } 

    public List<T> load(int first, int pageSize, List<SortMeta> multiSortMeta, Map<String,String> filters) { 
     throw new UnsupportedOperationException("Lazy loading is not implemented."); 
    } 

    public T getRowData(String rowKey) { 
     throw new UnsupportedOperationException("getRowData(String rowKey) must be implemented when basic rowKey algorithm is not used."); 
    } 

    public Object getRowKey(T object) { 
     throw new UnsupportedOperationException("getRowKey(T object) must be implemented when basic rowKey algorithm is not used."); 
    } 
} 

-------------編輯完---------------------

我已經創建了

public class LazyRetiDataModel<T> extends LazyDataModel<Rete> { 

    public void setFilters(Map<String, String> filters) { 
     this.qbeFilters = filters; 
    } 
} 

我必須用懶惰模型

private LazyDataModel<Rete> lazyModel; 
lazyModel = new LazyRetiDataModel<>(cfgRetePstnTAB); 

在我的代碼有

Map<String, String> mappa = ABAcus.createMap(p1,p2, p3, p4, p5); 

if (lazyModel != null) { 
      ((LazyRetiDataModel) lazyModel).setFilters(mappa); 
} 

我得到這樣的警告

warning: [unchecked] unchecked call to setFilters(Map<String,String>) as a member of the raw type LazyRetiDataModel 
       ((LazyRetiDataModel) lazyModel).setFilters(mappa); 

正確的，因爲LazyRetiDataModel<T> extends LazyDataModel<Rete>所以我((LazyRetiDataModel<?>) lazyModel).setFilters(mappa);

解決

但是?是正確的。？

---

解決的正確答案是

湯姆Hawtin提出的建議，馬克·彼得斯還與他的話改變了我的視野。 我定義

private LazyRetiDataModel lazyModel; 

反正Luiggi門多薩和保羅Bellora給我講起了泛型的一個重要想法，我認爲階級的正確定義是

public class LazyRetiDataModel extends LazyDataModel<Rete> { 

LazyRetiDataModel不使用泛型。

Answer 1

湯姆霍金，馬克彼得也用他的話提出的建議改變了我的視野。我定義了

private LazyRetiDataModel lazyModel; 反正Luiggi門多薩和保羅Bellora給我講起了泛型的一個重要想法，我認爲階級的正確定義是

公共類LazyRetiDataModel擴展LazyDataModel { LazyRetiDataModel不使用泛型。

java仿製藥基底

Answer 2

您收到警告是因爲您正在投射到原始類型LazyRetiDataModel。我會建議不要使用以下：

if (lazyModel != null) { 
    ((LazyRetiDataModel<Rete>)lazyModel).setFilters(mappa); 
} 

通常情況下，這將導致一個未經檢查的投警告，但其實這是一個例外，該規則，因爲編譯器已經知道泛型類型爲Rete。

請注意，我也同意Luiggi Mendoza對LazyRetiDataModel<T> extends LazyDataModel<Rete>的評論，可能是一個錯字 - 你想要LazyRetiDataModel<T> extends LazyDataModel<T>。

Answer 3

爲什麼public class LazyRetiDataModel<T>是通用的？它爲超類定義了泛型參數，如果這是它的唯一方法（setFilters），那麼只需簡單地刪除它。 更新： 如果沒有使用新定義的泛型方法，則應刪除它。正如你所提到的，它覆蓋了一些不能使用新的方法（如果我是正確的），所以我仍然認爲你可能不需要新的方法。