第十四天，java之父类类型和子类类型之间的转换

一、父类引用强转成为子类引用 

package learn20180720;

public class People {

	private String name;
	private Integer age;
	private Double height;
	
	public People(){
		this.name = "";
		this.age = 0 ;
		this.height = 0.0;
	}

	public People(String name, Integer age, Double height) {
		super();
		this.name = name;
		this.age = age;
		this.height = height;
	}

	public String getName() {
		return name;
	}

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

	public Integer getAge() {
		return age;
	}

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

	public Double getHeight() {
		return height;
	}

	public void setHeight(Double height) {
		this.height = height;
	}
	
	public void  tellObjectName(People p) {
		System.err.println(p.name);
	}
	
	public void sayInformation() {
		System.err.println("我的名字叫做："+this.name+"我的年龄是："+this.age+"我的身高是"+this.height);
	}
}

package learn20180720;

public class Chinese extends People{
	
	private String country;
	
	public Chinese(){
		super();
		country = "";
	}
	
	public Chinese(String aname,Integer aage,Double aheight) {
		super(aname,aage,aheight);
		this.country = "中国";
	}

	public String getCountry() {
		return country;
	}

	public void setCountry(String country) {
		this.country = country;
	}


	public void sayInformation() {
		// TODO Auto-generated method stub
		System.err.println("我的名字叫做："+this.getName()+"   我的年龄是："+this.getAge()+"   我的身高是："+this.getHeight()+"   我的国家是："+this.country);
	}
	
	
	
}

package learn20180720;

public class TestPeCh {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		People p1 = new Chinese();
		
		Chinese c1 = (Chinese)p1;
		
	}
	


}

可以看到，p1无法访问子类中的特有的方法（父类引用可以访问子类中重写父类中的方法），但是强转成为子类类型的引用c1之后，c1就可以访问子类中所有的方法啦。

 

---

二、父类不可以强转成为子类

 

package learn20180720;

public class TestPeCh {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		People p1 = new People();
		
		Chinese c1 = (Chinese)p1;

	}
	


}

报错了！