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)
2.1 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() {
}
@Override
public 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
@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
}3.2.1 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
@Override
public 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
如果父类方法的返回值类型是基本数据类型，那么子类重写的方法的返回值类型也必须是相应的基本数据类型
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(){
}
@Override
public 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(){
}
@Override
public 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(){
}
@Override
public 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
3.3.1 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
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