J2SE（七）Java之类的实例化

Java中创建（实例化）对象的五种方式
1、用new语句创建对象；
2、运用反射手段,调用java.lang.Class或者java.lang.reflect.Constructor类的newInstance()实例方法。如：Object obj = Class.forName("java.lang.Object").newInstance();
4、调用对象的clone()方法。
5、通过I/O流（包括反序列化），如运用反序列化手段，调用java.io.ObjectInputStream对象的 readObject()方法。

请看如下例子：

package com.review;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

public class TestClone implements Cloneable, Serializable {

	private static final long serialVersionUID = -3859091253969968165L;

	private int age;

	private String name;

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public TestClone(int age, String name) {
		this.age = age;
		this.name = name;
	}

	public TestClone() {
		super();
	}

	@Override
	protected Object clone() throws CloneNotSupportedException {
		// TODO Auto-generated method stub
		return super.clone();
	}
	
	@Override
	public String toString() {
		return "TestClone [age=" + age + ", name=" + name + "]";
	}

	public static void main(String[] args) throws CloneNotSupportedException,
			InstantiationException, IllegalAccessException,
			ClassNotFoundException, IOException {
		// new
		TestClone tc = new TestClone(18, "obj1");
		// clone
		TestClone tc2 = (TestClone) tc.clone();
		// newInstance
		TestClone tc3 = (TestClone) Class.forName("com.review.TestClone")
				.newInstance();
		// I/O
		FileOutputStream fos = new FileOutputStream("testClone.tmp");
		ObjectOutputStream oos = new ObjectOutputStream(fos);
		oos.writeObject(tc);
		oos.close();
		fos.close();

		FileInputStream fis = new FileInputStream("testClone.tmp");
		ObjectInputStream ois = new ObjectInputStream(fis);

		TestClone tc4 = (TestClone) ois.readObject();
		ois.close();
		fis.close();
		System.out.println(tc.toString());
		System.out.println(tc2.toString());
		System.out.println(tc3.toString());
		System.out.println(tc4.toString());
	}
}

结果集如下：

TestClone [age=18, name=obj1]
TestClone [age=18, name=obj1]
TestClone [age=0, name=null]
TestClone [age=18, name=obj1]

在调用newInstance方法时，调用的是TestClone的无参构造方法，所以age跟name都显示的是默认值。