Java学习day010（oop）：向上造型

秒速五厘米 2023-07-25 09:24 15阅读 0赞

#### 一、引用类型之间画等号 ####

\*\*引用类型变量之间画等号：\*\*指向同一个对象，通过一个引用对数据的修改会影响另一个引用对于数据的访问  
eg：房子钥匙  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpdHRlcl9t_size_16_color_FFFFFF_t_70]  
\*\*基本类型变量之间画等号：\*\*仅仅只做了个赋值操作，对一个变量的修改是不会影响另一个变量的  
eg：身份证复印件  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpdHRlcl9t_size_16_color_FFFFFF_t_70 1]

#### 二、向上造型 ####

**1. 超类型的引用指向派生类的对象  
2. 能点出来什么，看引用的类型**

class Animal{ 
    }
    class Tiger extends Animal{ 
    }
    class Lion extends Animal{ 
    }
    Animal o1=new Animal();//一个动物对象时动物类型的（动物是动物）
    Tiger o2=new Tiger();//老虎是老虎
    Animal o3=new Tiger();//一个老虎对象是动物类型的
    //超类 指向 派生类 （向上造型）
    //o3.只能点出animal类中的
    
    Tiger o4=new Animal();//动物是老虎——语义不通（编译错误）
    //继承要符合 is a（是一个）的关系

FlyingObject[]enemies;//等价于下面一行代码
    FlyingObject[]enemies=null;
    
    FlyingObject[]enemies={ };//等价于下面一行代码
    FlyingObject[]enemies=new FlyingObject[0];

##### 练习 #####

/*5 FlyingObject[]enemies;//等价于下面一行代码 FlyingObject[]enemies=null; FlyingObject[]enemies={};//等价于下面一行代码 FlyingObject[]enemies=new FlyingObject[0]; void action(){ System.out.println(enemies.length); } ex x=new ex(); x.action();*/
    	/*4 FlyingObject[]enemies;//等价于下面一行代码 FlyingObject[]enemies=null; FlyingObject[]enemies={};//等价于下面一行代码 FlyingObject[]enemies=new FlyingObject[0]; void action(){ System.out.println(enemies.length); } ex x=new ex(); x.action();*/
    	/*3FlyingObject[]enemies;//等价于下面一行代码 FlyingObject[]enemies=null; FlyingObject[]enemies={};//等价于下面一行代码 FlyingObject[]enemies=new FlyingObject[0]; void action(){ System.out.println(enemies.length); } ex x=new ex(); x.action();*/
    	/*2FlyingObject[]enemies;//等价于下面一行代码 FlyingObject[]enemies=null; FlyingObject[]enemies={};//等价于下面一行代码 FlyingObject[]enemies=new FlyingObject[0]; void action(){ System.out.println(enemies.length); } ex x=new ex(); x.action();*/
    	/*1FlyingObject[]enemies;//等价于下面一行代码 FlyingObject[]enemies=null; FlyingObject[]enemies={};//等价于下面一行代码 FlyingObject[]enemies=new FlyingObject[0]; void action(){ System.out.println(enemies.length); } ex x=new ex(); x.action();*/

/*5public class Test { public static void main(String[] args) { Student[] stus; stus=new Student[3]; stus[0]=new Student("zs",25,"lf",111); stus[1]=new Student("zz",21,"ss",112); stus[2]=new Student("ss",22,"dd",113); for(int i=0;i<stus.length;i++){ System.out.println(stus[i].name); stus[i].sayhi(); } Teacher[]tcs=new Teacher[3]; tcs[0]=new Teacher("sa",54, "kk", 5000); tcs[1]=new Teacher("ss",33, "aa", 3000); tcs[2]=new Teacher("saa",44, "ss", 4000); for(int i=0;i<tcs.length;i++){ System.out.println(tcs[i].name); tcs[i].sayhi(); } Doctor[]dts=new Doctor[3]; dts[0]=new Doctor("ss",54, "kk", "s"); dts[1]=new Doctor("sa",33, "aa", "a"); dts[2]=new Doctor("swa",44, "ss", "b"); for(int i=0;i<dts.length;i++){ System.out.println(dts[i].name); dts[i].sayhi(); } } } class Person{ int age; String name; String address; Person(String name,int age ,String address){ this.address=address; this.age=age; this.name=name; } void sayhi(){ System.out.println("hi my name:"+name+";age;"+age+";address:"+address); } } class Student extends Person{ int stuid; Student(String name,int age,String address,int stuid){ super(name,age,address); this.stuid=stuid; } } class Teacher extends Person{ int slary; Teacher(String name,int age,String address,int slary){ super(name,age,address); this.slary=slary; } } class Doctor extends Person{ String leavel; Doctor(String name,int age,String address,String leavel){ super(name,age,address); this.leavel=leavel; } }*/
    /*4 public class Test { public static void main(String[] args) { Student[] stus; stus=new Student[3]; stus[0]=new Student("zs",25,"lf",111); stus[1]=new Student("zz",21,"ss",112); stus[2]=new Student("ss",22,"dd",113); for(int i=0;i<stus.length;i++){ System.out.println(stus[i].name); stus[i].sayhi(); } Teacher[]tcs=new Teacher[3]; tcs[0]=new Teacher("sa",54, "kk", 5000); tcs[1]=new Teacher("ss",33, "aa", 3000); tcs[2]=new Teacher("saa",44, "ss", 4000); for(int i=0;i<tcs.length;i++){ System.out.println(tcs[i].name); tcs[i].sayhi(); } Doctor[]dts=new Doctor[3]; dts[0]=new Doctor("ss",54, "kk", "s"); dts[1]=new Doctor("sa",33, "aa", "a"); dts[2]=new Doctor("swa",44, "ss", "b"); for(int i=0;i<dts.length;i++){ System.out.println(dts[i].name); dts[i].sayhi(); } } } class Person{ int age; String name; String address; Person(String name,int age ,String address){ this.address=address; this.age=age; this.name=name; } void sayhi(){ System.out.println("hi my name:"+name+";age;"+age+";address:"+address); } } class Student extends Person{ int stuid; Student(String name,int age,String address,int stuid){ super(name,age,address); this.stuid=stuid; } } class Teacher extends Person{ int slary; Teacher(String name,int age,String address,int slary){ super(name,age,address); this.slary=slary; } } class Doctor extends Person{ String leavel; Doctor(String name,int age,String address,String leavel){ super(name,age,address); this.leavel=leavel; } }*/
    /*3 public class Test { public static void main(String[] args) { Student[] stus; stus=new Student[3]; stus[0]=new Student("zs",25,"lf",111); stus[1]=new Student("zz",21,"ss",112); stus[2]=new Student("ss",22,"dd",113); for(int i=0;i<stus.length;i++){ System.out.println(stus[i].name); stus[i].sayhi(); } Teacher[]tcs=new Teacher[3]; tcs[0]=new Teacher("sa",54, "kk", 5000); tcs[1]=new Teacher("ss",33, "aa", 3000); tcs[2]=new Teacher("saa",44, "ss", 4000); for(int i=0;i<tcs.length;i++){ System.out.println(tcs[i].name); tcs[i].sayhi(); } Doctor[]dts=new Doctor[3]; dts[0]=new Doctor("ss",54, "kk", 01); dts[1]=new Doctor("sa",33, "aa", 02); dts[2]=new Doctor("swa",44, "ss", 03); for(int i=0;i<dts.length;i++){ System.out.println(dts[i].name); dts[i].sayhi(); } } } class Person{ int age; String name; String address; Person(String name,int age,String address){ this.name=name; this.age=age; this.address=address; } void sayhi(){ System.out.println(name+age+address); } } class Student extends Person{ int suit; Student(String name,int age,String address,int suit){ super(name,age,address); this.suit=suit; } } class Teacher extends Person{ int slary; Teacher(String name,int age,String address,int slary){ super(name,age,address); this.slary=slary; } } class Doctor extends Person{ int leavel; Doctor(String name,int age,String address,int leavel){ super(name,age,address); this.leavel=leavel; } }*/
    /*2 public class Test { public static void main(String[] args) { Student[] stus; stus=new Student[3]; stus[0]=new Student("zs",25,"lf",111); stus[1]=new Student("zz",21,"ss",112); stus[2]=new Student("ss",22,"dd",113); for(int i=0;i<stus.length;i++){ System.out.println(stus[i].name); stus[i].sayhi(); } Teacher[]tcs=new Teacher[3]; tcs[0]=new Teacher("sa",54, "kk", 5000); tcs[1]=new Teacher("ss",33, "aa", 3000); tcs[2]=new Teacher("saa",44, "ss", 4000); for(int i=0;i<tcs.length;i++){ System.out.println(tcs[i].name); tcs[i].sayhi(); } Doctor[]dts=new Doctor[3]; dts[0]=new Doctor("ss",54, "kk", "s"); dts[1]=new Doctor("sa",33, "aa", "a"); dts[2]=new Doctor("swa",44, "ss", "b"); for(int i=0;i<dts.length;i++){ System.out.println(dts[i].name); dts[i].sayhi(); } } } class Person{ int age; String name; String address; Person(String name,int age,String address){ this.address=address; this.name=name; this.age=age; } void sayhi(){ System.out.println(name+age+address); } } class Student extends Person{ int suit; Student(String name,int age,String address,int suit){ super(name,age,address); this.suit=suit; } } class Teacher extends Person{ int slary; Teacher(String name,int age,String address,int slary){ super(name,age,address); this.slary=slary; } } class Doctor extends Person{ String levael; Doctor(String name,int age,String address,String levael){ super(name,age,address); this.levael=levael; } }*/
    /*1 public class Test { public static void main(String[] args) { Student[] stus; stus=new Student[3]; stus[0]=new Student("zs",25,"lf",111); stus[1]=new Student("zz",21,"ss",112); stus[2]=new Student("ss",22,"dd",113); for(int i=0;i<stus.length;i++){ System.out.println(stus[i].name); stus[i].sayhi(); } Teacher[]tcs=new Teacher[3]; tcs[0]=new Teacher("sa",54, "kk", 5000); tcs[1]=new Teacher("ss",33, "aa", 3000); tcs[2]=new Teacher("saa",44, "ss", 4000); for(int i=0;i<tcs.length;i++){ System.out.println(tcs[i].name); tcs[i].sayhi(); } Doctor[]dts=new Doctor[3]; dts[0]=new Doctor("ss",54, "kk", "s"); dts[1]=new Doctor("sa",33, "aa", "a"); dts[2]=new Doctor("swa",44, "ss", "b"); for(int i=0;i<dts.length;i++){ System.out.println(dts[i].name); dts[i].sayhi(); } } } class Person{ int age; String name; String address; Person(String name,int age,String address){ this.address=address; this.age=age; this.name=name; } void sayhi(){ System.out.println(name+age+address); } } class Student extends Person{ int nub; Student(String name,int age,String address,int nub){ super(name,age,address); this.nub=nub; } } class Doctor extends Person{ String leavel; Doctor(String name,int age,String address,String leavel){ super(name,age,address); this.leavel=leavel; } } class Teacher extends Person{ int slary; Teacher(String name,int age,String address,int slary){ super(name,age,address); this.slary=slary; } }*/

class moo{ 
    	int a;
    	void show(){ 
    		
    	}
    }
    class noo extends moo{ 
    	int b;
    	void test(){ 
    		
    	}
    }
    
    public class asdasd { 
    
    	public static void main(String[] args) { 
    
    		moo o1=new noo();
    		o1.a=2;
    		o1.show();
    		/*5 aoo o2=new boo(); o2.a=3; o2.show();*/
    		/*4aoo o3=new boo(); o3.a=4; o3.show();*/
    		/*3aoo o4=new boo(); o4.a=5; o4.show();*/
    		/*2aoo o5=new boo(); o5.a=6; o5.show();*/
    		/*1aoo o6=new boo(); o6.a=7; o6.show();*/
    	}
    
    }
    /*5 class Aoo{ int a; void show(){ } } class boo{ int b; void test(){ } }*/
    /*4 class Aoo{ int a; void show(){ } } class boo{ int b; void test(){ } } */
    /*3class Aoo{ int a; void show(){ } } class boo{ int b; void test(){ } } */
    /*2class Aoo{ int a; void show(){ } } class boo{ int b; void test(){ } } */
    /*1class Aoo{ int a; void show(){ } } class boo{ int b; void test(){ } }*/

Person[]ps=new Person[7];
    		ps[0]=new Student("zs",12,"sa","112");
    		ps[1]=new Student("ls", 13, "asd", "113");
    		ps[2]=new Student("xc", 14, "vb", "114");	
    		ps[3]=new Teacher("lk", 44, "lki", 7000);
    		ps[4]=new Teacher("lgy", 66, "sk", 35000);
    		ps[5]=new Doctor("asd",21,"asd","s");
    		ps[6]=new Doctor("ss",43,"cv","a");
    		for(int i=0;i<ps.length;i++){ 
    			System.out.println(ps[i].name);
    			ps[i].sayhi();
    		}
    		/*5 Person[]ps=new Person[6]; * ps[0]=new Student("zs",25,"yt","111"); * ps[1]=new Student("ll",23,"rt","112"); * ps[2]=new Teacher("lz",55,"lk",5555); * ps[3]=new Teacher("ww",44,"jh",6666); * ps[4]=new Doctor("az",45,"gf","s"); * ps[5]=new Doctor("er",56,"ds","a"); * for(int i=0;i<ps.length;i++){ System.out.println(ps[i].name); ps[i].sayhi(); } */
    		/*4Person[]ps=new Person[6]; ps[o]=new Student("sa",45,"sa","12212"); ps[1]=new Student("ds",42,"sd","12213"); ps[2]=new Teacher("sda",45,"sa",5000); ps[3]=new Teacher("saa",45,"sa",6000); ps[4]=new Doctor("sa",45,"sa","s"); ps[5]=new Doctor("sa",45,"sa","a"); for(int i=0;i<ps.length;i++){ System.out.println(ps[i].name); ps[i].sayhi(); }*/
    		/*3Person[]ps=new Person[3]; ps[0]=new Student("as",32,"sd","212121"); ps[1]=new Teacher("ass",32,"sd",10000); ps[2]=new Doctor("as",45,"we","a"); for(int i=0;i<ps.length;i++){ System.out.println(ps[i].name); ps[i].sayhi(); }*/
    		/*2 Person[]ps=new Person[3]; ps[0]=new Student("ew",32,"sd","455412"); ps[1]=new Teacher("ares",32,"gd",12000); ps[2]=new Doctor("afd",45,"wf","s"); for(int i=0;i<ps.length;i++){ System.out.println(ps[i].name); ps[i].sayhi(); }*/
    		/*1 Person[]ps=new Person[3]; * ps[0]=new Student("SA",45,"sda","212121"0; * ps[1]=new Doctor("DF",12,"asd","a"); * ps[2]=new Teacher("zxc",21,"SAd",544554); * for(int i=0;i<ps.length;i++){ * System.out.println(ps[i].length); * ps[i].sayhi(); * } */

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