Serializable如何保存文件上的對象編輯或清空並重新填充（看看ex）？

Question

我有地圖收集這樣的：

Map<File,Boolean> status = new HashMap<File,Boolean>(); 

它寫使用序列化的話，我必須通過添加新元素
或刪除一個或多個元素編輯採集（狀態）到文件。

通過添加和刪除元素來進行可序列化編輯（只是將已更改的東西寫入文件）或清空它並將其重新填充爲對象？
以及如何（如果我可以）添加或刪除文件中的元素？

對於任何不清楚的東西問我plz

Answer 1

不可能刪除文件的一部分。每當您在地圖中進行更改時，您都必須覆蓋整個文件。看我的例子：

import java.io.BufferedInputStream; 
import java.io.BufferedOutputStream; 
import java.io.File; 
import java.io.FileInputStream; 
import java.io.FileOutputStream; 
import java.io.IOException; 
import java.io.InputStream; 
import java.io.ObjectInputStream; 
import java.io.ObjectOutputStream; 
import java.io.OutputStream; 
import java.io.Serializable; 
import java.util.HashMap; 
import java.util.Map; 

public class SerializationProgram { 

    public static void main(String[] args) throws Exception { 
     emptyTest(); 
     addAndRemoveTest(); 
    } 

    private static void emptyTest() throws Exception { 
     ObjectSerializer serializer = new ObjectSerializer(); 
     serializer.serialize(new FileStatus()); 
     FileStatus persisted = serializer.deserialize(FileStatus.class); 
     test(persisted, new FileStatus()); 
    } 

    private static void addAndRemoveTest() throws Exception { 
     ObjectSerializer serializer = new ObjectSerializer(); 
     FileStatus toPersist = new FileStatus(); 
     FileStatus mirror = new FileStatus(); 

     toPersist = serializeDeserializeAndTest(serializer, toPersist, mirror); 

     File file = new File("/test/test.txt"); 
     Boolean status = Boolean.TRUE; 

     // Add file status 
     toPersist.addOrChangeStatus(file, status); 
     mirror.addOrChangeStatus(file, status); 

     toPersist = serializeDeserializeAndTest(serializer, toPersist, mirror); 

     // remove file status 
     toPersist.removeStatus(file); 
     mirror.removeStatus(file); 

     toPersist = serializeDeserializeAndTest(serializer, toPersist, mirror); 
     toPersist = serializeDeserializeAndTest(serializer, toPersist, mirror); 
    } 

    private static FileStatus serializeDeserializeAndTest(
      ObjectSerializer serializer, FileStatus toPersist, FileStatus mirror) 
      throws Exception { 
     serializer.serialize(toPersist); 
     toPersist = serializer.deserialize(FileStatus.class); 
     test(toPersist, mirror); 
     return toPersist; 
    } 

    private static void test(FileStatus given, FileStatus expected) { 
     if (given.equals(expected)) { 
      System.out.println("everything is OK"); 
     } else { 
      throw new IllegalArgumentException("Are not the same!"); 
     } 
    } 
} 

class ObjectSerializer { 

    private static final boolean OVERWRITE_MODE = false; 

    public <T> void serialize(T instance) throws IOException { 
     OutputStream overwriteStream = new FileOutputStream(getFile(instance.getClass()), OVERWRITE_MODE); 
     OutputStream bufferedStream = new BufferedOutputStream(overwriteStream); 
     ObjectOutputStream objectstream = new ObjectOutputStream(bufferedStream); 
     objectstream.writeObject(instance); 
     objectstream.close(); 
    } 

    @SuppressWarnings("unchecked") 
    public <T> T deserialize(Class<T> clazz) throws Exception { 
     InputStream input = new BufferedInputStream(new FileInputStream(getFile(clazz))); 
     ObjectInputStream objectStream = new ObjectInputStream(input); 
     T instance = (T) objectStream.readObject(); 
     objectStream.close(); 
     return instance; 
    } 

    private <T> File getFile(Class<T> clazz) { 
     return new File(clazz.getName()); 
    } 
} 

class FileStatus implements Serializable { 

    private static final long serialVersionUID = 1L; 

    Map<File, Boolean> statusMap = new HashMap<File, Boolean>(); 

    public void addOrChangeStatus(File file, boolean status) { 
     statusMap.put(file, status); 
    } 

    public void removeStatus(File file) { 
     statusMap.remove(file); 
    } 

    @Override 
    public int hashCode() { 
     final int prime = 31; 
     int result = 1; 
     result = prime * result 
       + ((statusMap == null) ? 0 : statusMap.hashCode()); 
     return result; 
    } 

    @Override 
    public boolean equals(Object obj) { 
     if (this == obj) 
      return true; 
     if (obj == null) 
      return false; 
     if (getClass() != obj.getClass()) 
      return false; 
     FileStatus other = (FileStatus) obj; 
     if (statusMap == null) { 
      if (other.statusMap != null) 
       return false; 
     } else if (!statusMap.equals(other.statusMap)) 
      return false; 
     return true; 
    } 
}