Java.io.ObjectInputStream.getField.get() 方法

描述

java.io.ObjectInputStream.getField.get(String name, long val) 方法从持久化字段中获取命名长字段的值。

声明

以下是 java.io.ObjectInputStream.getField.get() 方法的声明。

public abstract long get(String name, long val)

参数

• name − 字段名称

• val − name 没有值时使用的默认值

返回值

此方法返回命名的 long 字段的值。

异常

• IOException − 如果从底层 InputStream 读取时出现 I/O 错误

• IllegalArgumentException − 如果名称类型不可序列化或字段类型不正确

示例

下面的例子展示了 java.io.ObjectInputStream.getField.get() 方法的使用。

package com.tutorialspoint;

import java.io.*;

public class ObjectInputStreamDemo implements Serializable {
   public static void main(String[] args) {
      try {
         // create a new file with an ObjectOutputStream
         FileOutputStream out = new FileOutputStream("test.txt");
         ObjectOutputStream oout = new ObjectOutputStream(out);

         // write something in the file
         oout.writeObject(new Example());
         oout.flush();
         oout.close();

         // create an ObjectInputStream for the file we created before
         ObjectInputStream ois = new ObjectInputStream(new FileInputStream("test.txt"));

         // read an object from the stream and cast it to Example
         Example a = (Example) ois.readObject();

         // print var of a
         System.out.println("" + a.var);

      } catch (Exception ex) {
         ex.printStackTrace();
      }
   }

   static public class Example implements Serializable {
      static long var = 76458l;
      
      // assign a new serialPersistentFields 
      private static final ObjectStreamField[] serialPersistentFields = {
         new ObjectStreamField("var", Long.TYPE)
      };

      private void readObject(ObjectInputStream in)
         throws IOException, ClassNotFoundException {

         // get the field and assign it at var
         ObjectInputStream.GetField fields = in.readFields();

         // get var
         var = fields.get("var", 0l);
      }

      private void writeObject(ObjectOutputStream out) throws IOException {

         // write into the ObjectStreamField array the variable string
         ObjectOutputStream.PutField fields = out.putFields();
         fields.put("var", var);
         out.writeFields();
      }
   }
}

让我们编译并运行上面的程序，这将产生下面的结果 −

76458