向上转型:子类转父类

Father father1=  new Son();

向下转型:父类转子类

Son son =  (Son)new Father (); // 这样是运行时会报错

Father father1 = new Son(); Son son1 = (Son) father1; // 这样不报错

 

 

通过写一个方法把父类转换为子类

class Father {    private String name;    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    /**     * 将当前对象转换为子类对象     *     * @param clazz 目标类型     * @return 目标对象     */    public 
     
       T to(Class
      
        clazz) {        T instance;        try {            instance = clazz.newInstance();        } catch (Exception e) {            throw new IllegalArgumentException("Failed to create " + clazz.getSimpleName() + " instance.", e);        }        instance.setName(this.getName());        return instance;    }}
      
     

 

public class Son extends Father {    private String age;    public String getAge() {        return age;    }    public void setAge(String age) {        this.age = age;    }    public static void main(String[] args) {        // 子类转父类,父类再转子类        // Father father = new Son();        // Son son = (Son) father;        // 父类直接转子类        // Son son =  (Son)new Father (); // 运行时会报错        // 父类通过方法转直接转子类        Father father = new Father();        Son son = father.to(Son.class);    }}