class Father{
    Father(){
        System.out.println("子類會(huì)調(diào)用Father的第一個(gè)構(gòu)造方法");
    }
}
class Son extends Father{
    //我沒(méi)在這寫(xiě)子類的構(gòu)造方法，但是編譯器默認(rèn)補(bǔ)上子類構(gòu)造方法，這里相當(dāng)于有個(gè)Son(){super(); }方法，當(dāng)然這個(gè)super（）不寫(xiě)也一樣
}
class Demo{
    public static void main(String[] args)
    {
               Son s = new Son();
    }
}

class Father{
    //父類的有參數(shù)構(gòu)造方法
    Father(String name){
        System.out.println("子類會(huì)調(diào)用Father的有參數(shù)構(gòu)造方法");
    }
}
class Son extends Father{
}
class Demo{
    public static void main(String[] args)
    {
        Son s = new Son();
    }
}

class Father{
    Father(String name){
        System.out.println("子類會(huì)調(diào)用Father的第二個(gè)構(gòu)造方法");
    }
}
class Son extends Father{
    Son(String name){
         super(name);
    }
}
class Demo{
    public static void main(String[] args)
    {
        Son s = new Son("接第二條");
    }
}

package com.hn.yuan.common;
/**
 * 有參構(gòu)造方法
 */
public class Student {
    private String name;
    private String age;
    public Student(String name, String age) {
        this.name = name;
        this.age = age;
    }
    public void setName(String name) {
        this.name = name;
    }
    public void setAge(String age) {
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public String getAge() {
        return age;
    }
    public void start(){
        System.out.println("我叫"+name+"今年"+age+"歲了");
    }
}

package com.hn.yuan.common;
public class Test {
    public static void main(String[] args) {
        //使用有參數(shù)的構(gòu)造方法實(shí)例化對(duì)象
        Student st=new Student("張三","18");
        st.start();
    }
}

package com.hn.yuan.common;
/**
 * 無(wú)參構(gòu)造方法
 */
public class Student {
    private String name;
    private String age;
    //含有 無(wú)參構(gòu)造方法
    public Student() {
        System.out.println("調(diào)用了無(wú)參構(gòu)造方法");
    }
    public void setName(String name) {
        this.name = name;
    }
    public void setAge(String age) {
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public String getAge() {
        return age;
    }
    public void start(){
        System.out.println("我叫"+name+"今年"+age+"歲了");
    }
}

package com.hn.yuan.common;
public class Test {
    public static void main(String[] args) {
        //使用有參數(shù)的構(gòu)造方法實(shí)例化對(duì)象
        Student st=new Student();
        System.out.println(st);
    }
}

//定義類Person1   自己不手動(dòng)添加任何無(wú)參或有參數(shù)構(gòu)造方法
class Person1{
    private int age;
    private String name;
    private String sex;
}
//定義類Person2   自己添加無(wú)參的構(gòu)造方法
class Person2{
    private int age;
    private String name;
    private String sex;
    public Person2(){
        System.out.println("無(wú)參構(gòu)造方法被調(diào)用");
    }
}
//定義類Person3   有參數(shù)的構(gòu)造方法
class Person3{
    private int age;
    private String name;
    private String sex;
    public Person3(String name, String sex, int age ){
        this.name = name;
        this.sex = sex;
        this.age = age;
    }
}
//定義類Person4   自己添加無(wú)參的構(gòu)造方法,和有參數(shù)的構(gòu)造方法
class Person4{
    private int age;
    private String name;
    private String sex;
    //不帶參數(shù)的構(gòu)造函數(shù)，可以被重載
    public Person4(){
        System.out.println("無(wú)參構(gòu)造方法被調(diào)用");
    }
    //帶參數(shù)對(duì)的構(gòu)造函數(shù)
    public Person4(String name, String sex, int age ){
        this.name = name;
        this.sex = sex;
        this.age = age;
    }
}
public class ObjectInit_2 {
    public static void main(String[] args) {
        Person1 person1 = new Person1();//編譯通過(guò)；①實(shí)例化Person對(duì)象    ②自動(dòng)調(diào)用構(gòu)造方法Person( )
        Person2 person2 = new Person2();//編譯通過(guò)；打印: 無(wú)參構(gòu)造方法被調(diào)用
        // 這樣寫(xiě)，編譯器會(huì)報(bào)錯(cuò)，原因是系統(tǒng)默認(rèn)的無(wú)參構(gòu)造方法被有參構(gòu)造方法覆蓋，編譯器不能再提供無(wú)參構(gòu)造方法
        Person3 person3 = new Person3();
        //Person4 person4 = new Person4();//編譯通過(guò)；打印: 無(wú)參構(gòu)造方法被調(diào)用
        Person4 person4 = new Person4("qzz", "man", 18);//編譯通過(guò)；
    }
}

class Father {
    public Father(String lastname) {
    }
}
class Son extends Father {
    public Son() {
        super("aaaa");// 這句必須有
// 可以寫(xiě)其他代碼
    }
}

class Father {
    public Father() {
    }
    public Father(String lastname) {
    }
}
class Son extends Father {
    public Son() {
        super();// 這句可以有也可以沒(méi)有，沒(méi)有寫(xiě)的話會(huì)自動(dòng)調(diào)用
        // 可以寫(xiě)其他代碼
    }
}

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <!--這里由于采用springboot管理version，所以沒(méi)有version標(biāo)簽-->
        </dependency>

package com.hn.yuan.common;
import lombok.AllArgsConstructor;
import lombok.Data;
/**
 *  lombok的使用
 */
@Data
@AllArgsConstructor
public class Student {
    private String name;
    private String age;
}

/**
 * 編譯前代碼
 */
@RequiredArgsConstructor
public class Student() {
    private String name;
    private String age;
}
/**
 * 編譯后代碼
 */
public class Student() {
    private String name;
    private String age;
    public Student() {
    }
}

/**
 * 編譯前代碼
 */
@RequiredArgsConstructor
public class Student() {
    private final String gender;
    private final Integer ages = 18;
    private String name;
    private String age;
}
/**
 * 編譯后代碼
 */
public class Student() {
    private final String gender;
    private final Integer ages = 18;
    private String name;
    private String age;
    public Student(String gender, String name, String age) {
        this.gender = gender;
        this.name = name;
        this.age = age;
    }
}