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

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  描述

  java.io.ObjectInputStream.getField.get(String name, double val)方法从持久性字段获取命名的double字段的值。
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  声明

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

   public abstract double get(String name, double val)

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  参数

  • name字段名称。
  • val如果name没有值，则使用默认值。
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  返回值

  此方法返回命名的double字段的值。
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  异常

  • IOException如果从基础InputStream读取时发生I / O错误。
  • IllegalArgumentException如果名称的类型不可序列化或字段类型不正确。
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  例子

  以下示例显示java.io.ObjectInputStream.getField.get()方法的用法。

   
  package com.jc2182; 
  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 double var = 1.875d;
        
        // assign a new serialPersistentFields 
        private static final ObjectStreamField[] serialPersistentFields = {
           new ObjectStreamField("var", Double.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", 0d);
        }
  
        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();
        }
     }
  }
  

  让我们编译并运行以上程序，这将产生以下结果-

   1.875