1. 使用new关键字

​ 采用new关键字实例化对象是Java中最为常见的方法，下面是采用new关键字实例化对象的示例。在开始之前，我们先准备好一个Java类：Student.java。

package com.ramostear.oops;public class Student{private String name;private String nickname;public Student(){super();}public Student(String name,String nickname){this.name = name;this.nickname = nickname;}public String getName(){return name;}public void setName(String name){this.name = name;}public String getNickname(){return nickname;}public void setNickname(String nickname){this.nickname = nickname;}}

接下来，我们通过new关键字来创建几个学生：

package com.ramostear.oops;
public class TestNewStudent{public static void main(String[] args){Student zhangsan = new Student("Zhangsan","张三");Student lisi = new Student();lisi.setName("Lisi");lisi.setNickname("李四")；}
}

2. 使用Class类的newInstance()方法

​ 首先，我们可以通过Class.forName()方法动态加载目标类，然后再调用newInstance()方法，动态实例化对象。同理，在开始之前，我们需要准备一个目标类：Student.java。

package com.ramostear.oops;
public class Student{private String name = "Zhangsan";private String nickname = "张三";public Student(){super();}public Student(String name,String nickname){super();this.name = name;this.nickname = nickname;}public String getName(){return name;}public void setName(String name){this.name = name;}public String getNickname(){return nickname;}public void setNickname(String nickname){this.nickname = nickname;}
}

接下来，将演示如何通过newInstance()方法来创建新的对象：

package com.ramostear.oops;
public class TestUseNewInstanceMethod{public static void main(String[] args){try{String className = "com.ramostear.oops.Student";Class clz = Class.forName(className);Student student = (Student) clz.newInstance();System.out.println("student name :"+ student.getName()+", nickname: "+student.getNickname());}catch(InstantiationException | IllegalAccessException | ClassNotFoundException e){e.printStackTrace();}}
}

运行main()方法，将输出如下信息：

student name :Zhangsan, nickname:张三

3. 使用Constructor.newInstance()方法

​ 与Class类的newInstance()方法相似，我们还可以使用java.lang.reflect.Constructor类的newInstance()方法来创建新的对象。同样，我们先准备一个目标类：

package com.ramostear.oops;
public class Student{private String name = "Constructor";private String nickname = "构造器";public Student(){super();}public Student(String name,String nickname){super();this.name = name;this.nickname = nickname;}public String getName(){return name;}public void setName(String name){this.name = name;}public String getNickname(){return nickname;}public void setNickname(String nickname){this.nickname = nickname;}
}

接下来，我们看看如何使用Constructor的newInstance()方法创建新的对象：

package com.ramostear.oops;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;public class UseConstructorNewInstanceMethod{public static void main(String[] args){Constructor<Student> studentConstructor;try{studentConstructor = Student.class.getConstructor();Student student = studentConstructor.newInstance();System.out.println("student name :"+ student.getName()+", nickname: "+student.getNickname());}catch(InstantiationException | IllegalAccessException | IllegalArgumentException | InvocationTargetException |NoSuchMethodException | SecurityException e){e.printStackTrace();}} 
}

执行main()方法，将在控制台输出如下信息：

student name:Constructor, nickname:构造器

4. 使用反序列化

​ 如果要使用反序列化创建对象，则目标类首先要实现Serializable接口。Serializable是一个标记接口。在本次示例中，我们先创建一个Student对象，并将其保存到data.txt文件中，然后在通过反序列化操作，读取data.txt中的数据，并创建新的对象。

package com.ramostear.oops;import java.io.Serializable;public class Student implements Serializable{private String name;private String nickname;public Student() {super();}public Student(String name, String nickname) {super();this.name = name;this.nickname = nickname;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getNickname() {return nickname;}public void setNickname(String nickname) {this.nickname = nickname;}
}

接下来，将通过一个简单的示例，演示如何使用反序列化的方式创建新的对象：

package com.ramostear.oops;import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;public class StudentDemo {public static void main(String[] args) {String filePath = "data.txt";Student student1 = new Student("Deserialization", "反序列化");try {FileOutputStream fileOutputStream = new FileOutputStream(filePath);ObjectOutputStream outputStream = new ObjectOutputStream(fileOutputStream);outputStream.writeObject(student1);outputStream.flush();outputStream.close();FileInputStream fileInputStream = new FileInputStream(filePath);ObjectInputStream inputStream = new ObjectInputStream(fileInputStream);Student student2 = (Student) inputStream.readObject();inputStream.close();System.out.println("Student name:"+student2.getName()+", nickname:"+student2.getNickname());} catch (Exception ee) {ee.printStackTrace();}}
}

执行上述代码，将在控制台输出如下信息：

Student name:Deserialization,nickname:反序列化

5. 使用对象克隆创建新的对象

​ clone()方法可以创建现有对象的副本，但在使用clone()方法前，需保证模板类实现了Cloneable接口，Cloneable接口也是一个标记类接口。下面是使用克隆方式创建新对象的完整示例：

package net.javaguides.corejava.oops;import java.io.Serializable;public class Student implements Cloneable {private String name;private String nickname;public Student() {super();}public Student(String name, String nickname) {super();this.name = name;this.nickname = nickname;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getNickname() {return nickname;}public void setNickname(String nickname) {this.nickname = nickname;}public static void main(String args[]) {Student stu1 = new Student("Clone", "克隆");try {Student stu2 = (Student) stu1.clone();System.out.println("Student name :"+stu2.getName()+",nickname:"+stu2.getNickanme());} catch (CloneNotSupportedException e) {e.printStackTrace();}}
}

运行上述代码，控制台将输出如下信息：

Student name： Clone,nickname:克隆

6. 使用sun.misc.Unsafe类的allocateInstance（)方法创建对象

class Person {private String name = "aaa";public void setName(String name) {this.name = name;}@Overridepublic String toString() {return "Person [name=" + name + "]";}}public class UnsafeClassTester {public static void main(String[] args) {try {java.lang.reflect.Field field = sun.misc.Unsafe.class.getDeclaredField("theUnsafe");field.setAccessible(true);sun.misc.Unsafe unsafe = (sun.misc.Unsafe) field.get(null);Person p = (Person) unsafe.allocateInstance(Person.class);p.setName("xxxxxx");System.out.println(p);} catch (Exception e) {e.printStackTrace();}}}