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

  • 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。
  • 声明

    以下是java.io.ObjectInputStream.getField.get()方法的声明。
     public abstract double get(String name, double val)
  • 参数

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

    此方法返回命名的double字段的值。
  • 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。
  • 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