解析java中的方法重写

1 含义

子类继承父类后,可以在子类中书写一个与父类同名同参的方法,从而实现对父类中同名同参数的方法的覆盖,我们把这一过程叫做方法的重写(override)

2 为什么要使用方法重写

2.1 当父类的方法满足不了子类的需求的时候,需要在子类中对该方法进行重写

2.2 题目与分析

例如存在一个父类Peple,子类Chinese,父类中有一个say()方法,输出人在说话,但是我想要的时子类时候调用时输出中国人在说话,很显然直接调用方法不行,所以需要在子类中对say方法进行方法的重写

2.3 示例代码

People类

public class Peple {private String name;private String sex;private int age;private int weight;public Peple() {}public Peple(String name, String sex, int age, int weight) {this.name = name;this.sex = sex;this.age = age;this.weight=weight;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public int getWeight() {return weight;}public void setWeight(int weight) {this.weight = weight;}public void say(){System.out.println("人在说话");}}

Chinese类

public class Chinese extends Peple{public Chinese() {}@Overridepublic void say() {System.out.println("中国人在说话");}
}

Test03类

public class Test03 {public static void main(String[] args) {Chinese c=new Chinese();c.say();//当进行方法重写时,调用的是子类的say()方法}
}

2.4 示例代码运行截图

3 如何使用方法重写

3.1 基本语法

@Override
权限修饰符 返回值类型 方法名(形参列表){//子类重写的方法的权限修饰符的访问权限必须大于等于父类的,但是父类不能是private//当父类的返回值类型为基本数据类型或者为void时,子类方法的返回值类型也应该为对应的基本数据类型或者void}

3.2 具体分析

3.2.1 子类重写的方法的访问权限应该大于等于父类方法的访问权限

a 示例代码

People类

public class Peple {private String name;private String sex;private int age;private int weight;public Peple() {}public Peple(String name, String sex, int age, int weight) {this.name = name;this.sex = sex;this.age = age;this.weight=weight;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public int getWeight() {return weight;}public void setWeight(int weight) {this.weight = weight;}//没有写访问权限的话,默认是default访问权限void say(){System.out.println("人在说话");}}

Chinese类

public class Chinese extends Peple{public Chinese(){}//父类say方法的访问权限为default,子类say方法的访问权限为public,// 符合子类方法访问权限大于等于父类方法访问权限的要求@Overridepublic void say() {System.out.println("中国人在说话");}
}

Test03类

public class Test03 {public static void main(String[] args) {Chinese c=new Chinese();c.say();}
}

b 示例代码运行截图

3.2.2 当父类方法的返回值类型为基本数据类型时,子类重写的方法的返回值类型也为对应的基本数据类型

a 示例代码

People类

public class Peple {private String name;private String sex;private int age;private int weight;public Peple() {}public Peple(String name, String sex, int age, int weight) {this.name = name;this.sex = sex;this.age = age;this.weight=weight;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public int getWeight() {return weight;}public void setWeight(int weight) {this.weight = weight;}public double add(int a,int b){return a+b;}}

Chinese类

public class Chinese extends Peple{public Chinese(){}@Overridepublic double add(int a,int b) {return a+b+1;}
}

Test03类

public class Test03 {public static void main(String[] args) {Chinese c=new Chinese();System.out.println("求和之和再加上1的结果为: "+c.add(2, 3));}
}

b 示例代码运行截图

3.2.3 当父类方法的返回值类型为void时,子类重写的方法的返回值类型也为void

a 示例代码

People类

public class Peple {private String name;private String sex;private int age;private int weight;public Peple() {}public Peple(String name, String sex, int age, int weight) {this.name = name;this.sex = sex;this.age = age;this.weight=weight;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public int getWeight() {return weight;}public void setWeight(int weight) {this.weight = weight;}public void eat(){System.out.println("人的主食一般是熟食");}}

Chinese类

public class Chinese extends Peple{public Chinese(){}@Overridepublic void eat() {System.out.println("中国人的主食是大米或者小麦");}
}

Test03类

public class Test03 {public static void main(String[] args) {Chinese c=new Chinese();c.eat();}
}

b 示例代码运行截图

3.2.4 当父类的方法被static修饰的时候,子类是不能重写该方法的

a 错误示例代码

People类

public class Peple {private String name;private String sex;private int age;private int weight;public Peple() {}public Peple(String name, String sex, int age, int weight) {this.name = name;this.sex = sex;this.age = age;this.weight=weight;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public int getWeight() {return weight;}public void setWeight(int weight) {this.weight = weight;}public static void eat(){System.out.println("人的主食一般是熟食");}}

Chinese类

public class Chinese extends Peple{public Chinese(){}@Overridepublic void eat() {System.out.println("中国人的主食是大米或者小麦");}
}

Test03类

public class Test03 {public static void main(String[] args) {Chinese c=new Chinese();c.eat();}
}

b 示例代码运行截图

编译时idea给出的错误提示

强制运行后给出的错误提示

3.3 方法重写的一些小技巧

3.3.1 复制法

步骤

1.先直接复制(Ctrl+C)父类中需要被子类重写的那个方法

2.粘贴(Ctrl+V)到子类中

3.修改子类中的功能,便于实现父类实现不了的需求

操作截图展示

3.3.2 编译器提示法

步骤

1.先在子类类体中,非方法内位置,写入一个英文@符号

2.选中提示中的Overide/implement methods…

3.双击后弹出一个重写方法选择列表弹窗

4.根据提示选中对应的需要重写的方法

5.点击ok按钮后会在子类中生成一个你选中方法的重写方法

6.把生成的重写方法中的自动生成的首行去掉,然后根据需求在方法体里面写入合适的语句

操作截图展示

3.3.3 快捷键法

步骤

1.把鼠标移动到重写方法应该生成的位置

2.同时按下键盘上的Alt键和Insert键,

3.在弹出框中,选中Override Methods

4.双击后会弹出一个界面,在界面中选中需要被子类重写的方法

5.点击OK按钮后会生成所需要的重写方法

6.去掉重写方法中自动生成的首行,然在其方法体里面写入合适的语句

操作截图展示