java对象实例化

JAVA类，只要知道了类名（全名）就可以创建其实例对象，通用的方法是直接使用该类提供的构造方法，如

NewObject o = new NewObject();

NewObject o = new NewObject("test");

NewObject o = new NewObject(new String[]{"aaa","bbb"});

除此之外，还可以利用java.lang.Class<T>类来实现JAVA类的实例化。

1、空构造方法

如果类有空构造方法，如下面的类

public class NewObject
{
 String name;
 
 public NewObject(String[] name)
 {
  this.name = name[0];

     System.out.println(“ the object is created!”);
 }
 
 public void write()
 {
  System.out.println(this.name);
 }
}

使用以下代码可实现实例化：

NewObject no = null;
 try
   {
    no = (NewObject)Class.forName(className).newInstance();

   no.write();
   }
   catch (InstantiationException e)
   {
    e.printStackTrace();
   }
   catch (IllegalAccessException e)
   {
    e.printStackTrace();
   }
   catch (ClassNotFoundException e)
   {
    e.printStackTrace();
   }

 

 

2、带参数构造方法

public class NewObject
{
 String name;
 
 public NewObject()
 {

     System.out.println(“ the object is created!”);
 }
 
 public void write()
 {
  System.out.println(“”);
 }
}

使用以下代码可实现实例化：

try
   {
    no = (NewObject)Class.forName(className).getConstructor(String.class).newInstance(names);

//no = (NewObject)Class.forName(className).getConstructor(new Object[]{String.class}).newInstance(names);
   }
   catch (IllegalArgumentException e)
   {
    e.printStackTrace();
   }
   catch (SecurityException e)
   {
    e.printStackTrace();
   }
   catch (InstantiationException e)
   {
    e.printStackTrace();
   }
   catch (IllegalAccessException e)
   {
    e.printStackTrace();
   }
   catch (InvocationTargetException e)
   {
    e.printStackTrace();
   }
   catch (NoSuchMethodException e)
   {
    e.printStackTrace();
   }
   catch (ClassNotFoundException e)
   {
    e.printStackTrace();
   }

 

 

3、带数组参数构造方法

public class NewObject
{
 String name;
 
 public NewObject(String name)
 {
  this.name = name; 

    System.out.println(“ the object is created!”);
 }
 
 public void write()
 {
  System.out.println(this.name);    
 }
}

使用以下代码可实现实例化：

try
   {
    Constructor[] cs;
    cs = Class.forName(className).getConstructors();
    Constructor cc = Class.forName(className).getConstructor(String[].class);
    no = (NewObject)cc.newInstance(new Object[]{names});
   }
   catch (SecurityException e)
   {
    e.printStackTrace();
   }
   catch (ClassNotFoundException e)
   {
    e.printStackTrace();
   }
   catch (NoSuchMethodException e)
   {
    e.printStackTrace();
   }
   catch (IllegalArgumentException e)
   {
    e.printStackTrace();
   }
   catch (InstantiationException e)
   {
    e.printStackTrace();
   }
   catch (IllegalAccessException e)
   {
    e.printStackTrace();
   }
   catch (InvocationTargetException e)
   {
    e.printStackTrace();
   }