1.什么是类:相同属性和方法的一组对象的集合
什么是对象:描述客观事物的一个实体,有一组属性和方法构成
方法和属性是什么:方法指的是:对象执行的操作;属性指的是:对象具有的各种特征
3.方法和属性是什么?方法:对象执行的操作
属性:对象具有的各种特征
方法重载:
1.方法名一样
2.参数列表不一样(参数个数不同或者参数类型不同)
代码:
- package com.lenovo.www.entity;
- /**
- * 方法重载
- *
- * @author lenovo1
- *
- */
- public class Essay {
- public void writeEssay() {
- System.out.println("无参方法");
- }
- public void writeEssay(String pencil, String paper) {
- System.out.println("用纸和笔写文章");
- }
- public void writeEssay(int a, String paper) {
- System.out.println("用"+a+"支笔写文章");
- }
- public void writeEssay(String a, int b) {
- System.out.println("用"+b+"张纸写文章");
- }
- public String writeEssay(String computer) {
- computer = computer+"写文章";
- return computer;
- }
- }
- package com.lenovo.www.entity;
- import java.util.Scanner;
- import javax.swing.plaf.synth.SynthSpinnerUI;
- /**
- *
- * @author lenovo1
- *
- */
- public class Test {
- public static void main(String[] args) {
- Essay essay = new Essay() ;
- essay.writeEssay(10,"aaa");
- essay.writeEssay("派克","A4纸");
- String s = essay.writeEssay("联想电脑");
- System.out.println(s);
- }
- }
5.Eclipse常用快捷键有哪些?
导包:ctrl+shift+O
代码格式化:ctrl+shift+F
代码提示:Alt+/ 注释:/**+Enter
注释代码:ctrl+/
注意:有的快捷键被输入法占用
6.什么叫实参:调用方法的时候,传递的参数叫实参
7.什么是形参:定义方法的时候,括号里面的参数叫形参
8.定义方法的语法格式
【权限修饰符】方法返回值类型 方法名(形参列表)
{
//由零条到多条可执行性语句组成的方法体
}
构造方法:是一种特殊的方法,其主要功能是用来在创建对象时初始化对象,即为对象成员变量赋初始值。
构造方法与类名相同,可以重载多个不同的构造方法。
构造方法没有返回类型,也不能定义为void,在方法名面前不能声明方法类型。
- public class Ex_animal {
- public static void main(String[] args) {
- // TODO Auto-generated method stub
- Animal an1 = new Animal("兔子","草",5);
- Animal an2 = new Animal();
- Animal an3 = new Animal(an1,an2);
- an2.all(an3);
- }
- }
- class Animal{
- String name;
- String eat;
- int weight;
- public Animal() {
- this.name = name;
- this.eat = "猪蹄";
- this.weight = 12;
- }
- public Animal(Animal a,Animal b) {
- this.name = b.name;
- this.eat = a.eat;
- this.weight = b.weight;
- }
- public Animal(String name,String eat,int weight) {
- this.name = name;
- this.eat = eat;
- this.weight = weight;
- }
- public Animal(String name,int weight) {
- this.name = name;
- this.weight = weight;
- }
- public void eat1() {
- System.out.println("这个动物喜欢吃" + this.eat);
- }
- public void run() {
- System.out.println("这个动物会跑");
- }
- public void all(Animal an) {
- System.out.println("这是一只 " + this.name + ",它喜欢吃 " + an.eat + ",它重 " + an.weight +" 斤");
- }
- }
- public class Test {
- public static void main(String[] args) {
- Animal dog = new Animal("小黑", "小猫", "黑色");
- Animal cat = new Animal("小白", "小狗", "白色");
- String s = dog.play(cat, dog);
- System.out.println("获胜的动物是" + s);
- }
- }
- class Animal {
- String name;
- String kind;
- int age;
- String color;
- long animalID;
- String date;
- public Animal(String name, String kind) {
- this.name = name;
- this.kind = kind;
- }
- public Animal(String name, String color, String kind) {
- this.name = name;
- this.color = color;
- this.kind = kind;
- }
- public Animal(String name, int age, long animalID) {
- this.age = age;
- this.animalID = animalID;
- }
- public String play(Animal dog, Animal cat) {
- System.out.println("这只" + dog.color + "是" + dog.name + "," + dog.kind + ",正在和那只" + cat.color + "叫做" + cat.name
- + "," + cat.kind + ",在打架");
- return cat.kind;
- }
- }