一、Java中创建(实例化)对象的五种方式
1、用new语句直接创建对象，这是最常见的创建对象的方法。
2、通过工厂方法返回对象，如:String str = String.valueOf(23);
3、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。
二.实例说明：
创建 Fruit（水果）实体类
package com.shine.demo.object;
import java.io.Serializable;
@SuppressWarnings("serial")
public class Fruit implements Serializable, Comparable<Fruit>{
/**
* id.
*/
private Long id;
/**
* 名称.
*/
private String name;
/**
* 价格.
*/
private Double price;
public Fruit() {
super();
}
public Fruit(Long id, String name, Double price) {
super();
this.id = id;
this.name = name;
this.price = price;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Double getPrice() {
return price;
}
public void setPrice(Double price) {
this.price = price;
}
@Override
public String toString() {
return "id为：" + this.getId() + ",的："+ this.getName() +"的价格为："+this.getPrice();
}
@Override
public int compareTo(Fruit otherFruit) {
if(!(this.id.equals(otherFruit.id)))
return this.id.compareTo(otherFruit.id);
else if(!(this.name.equals(otherFruit.name)))
return this.name.compareTo(otherFruit.name);
else if(this.price.equals(otherFruit.price))
return this.price.compareTo(otherFruit.price);
return 0;
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((id == null) ? 0 : id.hashCode());
result = prime * result + ((name == null) ? 0 : name.hashCode());
result = prime * result + ((price == null) ? 0 : price.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (!(obj instanceof Fruit))
return false;
Fruit other = (Fruit) obj;
return this.id.equals(other.id) && this.name.equals(other.name) && this.price.equals(other.price);
}
}
测试说明 : 下面主要对1/3方式进行说明
package com.shine.demo.object;
public class ObjOpen {
public static void main(String[] args) {
/**方法一 ： new语句直接创建对象 */
Fruit fruit = new Fruit(1L,"苹果",4.3);
System.out.println(fruit.toString());
/**方法三 ：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();
**/
try {
Fruit fruit2 = (Fruit) Class.forName("com.shine.demo.object.Fruit").newInstance();
fruit2.setId(2L);
fruit2.setName("香蕉");
fruit2.setPrice(2.6);
System.out.println(fruit2);
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
}
三、结果：