java 构造器

概念

在这里插入图片描述

案例1

在这里插入图片描述

package lesson.l11_oop2;/*** Illustration** @author DengQing* @version 1.0* @datetime 2022/7/3 15:28* @function*/
public class Person {private int age;private String name;public Person() {this.age = 18;}public Person(int age, String name) {this.age = age;this.name = name;}public void setAge(int age) {
/*        if (age<0||age>130){throw new RuntimeException("传入的数据非法");}this.age=age;*/if (age >= 0 && age <= 130) {this.age = age;} else {
//            this.age = 0;throw new RuntimeException("传入的数据非法");}}public int getAge() {return this.age;}
}class PersonTest {public static void main(String[] args) {Person person = new Person();person.setAge(9);System.out.println(person.getAge());Person person1 = new Person();System.out.println(person1.getAge());Person person2 = new Person(30, "dq");System.out.println(person2.getAge());}
}

案例2

在这里插入图片描述
海伦公式：
已知三角形三边a,b,c，则：
p=(a+b+c)/2
S=sqrt[p(p-a)(p-b)(p-c)]

package lesson.l11_oop2;/*** Illustration** @author DengQing* @version 1.0* @datetime 2022/7/3 16:22* @function*/
public class TriAngle {private Double base;private Double height;public TriAngle() {}public TriAngle(Double base, Double height) {this.base = base;this.height = height;}public Double getBase() {return this.base;}public Double getHeight() {return this.height;}public Double getArea() {return (this.base*this.height)/2;}
}