在本篇文章中,将介绍5种创建JAVA对象的方式。类是创建对象的基本模板,接下来将介绍5种不同的方式,利用Java类来实例化Java对象。
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(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");
}
}
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
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
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
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