构造器

创建对象时，会创建构造器

package com.itheima.constructor;

public class Test {
    public static void main(String[] args) {
        Student s1 = new Student("张三", 99);
        System.out.println(s1.name);
        System.out.println(s1.score);
    }
}

package com.itheima.constructor;

public class Student {
    String name;
    double score;

    public Student() {
        System.out.println("无参数构造器执行了");
    }

    public Student(String name, double score) {
        System.out.println("有参数构造器执行了");
        this.name = name;
        this.score = score;
    }
}

• this指向当前的对象
• 当没有写constructor构造器时，创建实例时会自动创建无参数的构造器
• 创建实例没有传参数，执行无参数构造器，否则执行有参数构造器