JAVA中实例化类的四种方法
1）使用new操作符
2）调用Class对象的newInstance()方法
3）调用clone()方法，对现有实例的拷贝
4）通过ObjectInputStream的readObject()方法反序列化类
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import java.io.*;
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import java.lang.reflect.Constructor;
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import java.lang.reflect.InvocationTargetException;
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class ClassInstance implements Cloneable, Serializable {
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private static final long serialVersionUID = -1261396803896758295L;
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private String str = "测试...";
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public void fun(){
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System.out.println(str);
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}
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public ClassInstance(String str){
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System.out.println("有参类的实例化");
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this.str += str;
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}
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public ClassInstance(){
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System.out.println("无参类的实例化");
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}
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public Object clone(){
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return this;
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}
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}
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public class ClassInstanceTest{
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public static void main(String[] args) throws ClassNotFoundException, InstantiationException,
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IllegalAccessException, IOException,InvocationTargetException, NoSuchMethodException{
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//第一种类的实例化方式
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ClassInstance ci01 = new ClassInstance("01");
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ci01.fun();
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//第二种类的实例化方式
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ClassInstance ci02 = (ClassInstance) Class.forName("ClassInstance").newInstance();
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ci02.fun();
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//第三种类的实例化方式
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ClassInstance ci03 = (ClassInstance) ci01.clone();
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ci03.fun();
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//第四种类的实例化方式
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FileOutputStream fos = new FileOutputStream("ci.tmp");
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ObjectOutputStream oos = new ObjectOutputStream(fos);
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oos.writeObject(ci01);
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oos.close();
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fos.close();
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FileInputStream fis = new FileInputStream("ci.tmp");
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ObjectInputStream ois = new ObjectInputStream(fis);
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ClassInstance ci04 = (ClassInstance) ois.readObject();
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ois.close();
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fis.close();
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ci04.fun();
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System.out.println("--------------------额外测试--------------------");
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ClassInstance ci05 = null;
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//额外的思考 在第二种类实例化的方式中有没有一种方法实现有参数的构造方式
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//获得类的构造信息
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Constructor[] ctor = Class.forName("ClassInstance").getDeclaredConstructors();
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//找到我们需要的构造方法
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for(int i=0;i<ctor.length;i++ ){
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Class[] cl = ctor[i].getParameterTypes();
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if(cl.length == 1){
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//实例化对象
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ci05 = (ClassInstance) Class.forName("ClassInstance").getConstructor(cl).newInstance(new Object[]{"05"});
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}
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}
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ci05.fun();
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}
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}
