上午Java课课堂笔记 Week18_1

☆今天学习主题
调用类方法 遍历 自定义java的方法…

Project1

import java.util.ArrayList;
//Object 
//集合 
public class Week18_1_1 {
    public static void main(String[] args) {
        // int[] arr={1,5,2};//hash值  按照线性顺序 元素可以重复  ：有序可重复
        ArrayList array1=new ArrayList();//集合可以动态改变长度
        System.out.println(array1);
        array1.add("小明");
        array1.add("小张");
        array1.add("小王");
        array1.add(123);
        array1.add(true);
        array1.add(1.2);
        array1.add(1.2);
        array1.add(1.2);
        System.out.println(array1);
        System.out.println(array1.get(0));//根据下标获得集合中具体某个元素
        System.out.println(array1.get(5));//根据下标获得集合中具体某个元素
        System.out.println(array1.size());//得到集合的长度
        //遍历集合
        binaLi(array1);
    }
    public static void binaLi(ArrayList array){
        for(int i=0;i<array.size();i++){
            System.out.print(array.get(i)+"  ");
        }
    }
}

运行输出结果1

Project 2

import java.util.ArrayList;
public class Week18_1_2 {
    public static void main(String[] args) {
        //ArrayList 查找方便(有序排列)，删除不方便
        ArrayList arrlist2=new ArrayList();
        arrlist2.add("赵云");
        arrlist2.add("曹操");
        arrlist2.add("孙尚香");
        arrlist2.add("周瑜");
        arrlist2.add("郭嘉");
        System.out.println(arrlist2);
        arrlist2.remove(2);//删除指定下标的元素
        System.out.println(arrlist2);
    }
}

Project 3

import java.util.LinkedList;
public class Week18_1_3 {
//linkedList
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        LinkedList linklist=new LinkedList();
        linklist.add("司马懿");
        linklist.add("邓艾");
        linklist.add("钟会");
        linklist.add("陆逊");
        linklist.add("陆逊");
        linklist.add("陆逊");
        System.out.println(linklist);
        linklist.remove(3);//删除指定下标的元素
        System.out.println(linklist);
        linklist.removeFirst();
        System.out.println(linklist);
    }
}

Project 4

import java.util.ArrayList;
import java.util.Iterator;
public class Week18_1_4 {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        ArrayList arraylist=new ArrayList();
        arraylist.add("郭嘉");
        arraylist.add("曹操");
        arraylist.add("许攸");
        arraylist.add("法正");
        arraylist.add("贾诩");
        System.out.println(arraylist);
        //集合的迭代器遍历
        Iterator iterator = arraylist.iterator();
        while(iterator.hasNext()){//hashnext迭代器有元素吗
            Object next = iterator.next();//next 取到这个元素  ， 也是 get的意思
            // Object next 多态   
            System.out.print(next+" ");
        }
        System.out.println();
        //第四种遍历 增强for循环
        for(Object xx:arraylist){
            System.out.print(xx+"  ");
        }
    }
}

import java.util.ArrayList;
public class Week18_1_5 {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Dog dog1 = new Dog("阿黄", 2);
        Dog dog2 = new Dog("阿花", 2);
        Dog dog3 = new Dog("阿明", 2);
        //集合加入泛型，<Dog>  
        ArrayList<Dog> arrayList = new ArrayList<Dog>();
        arrayList.add(dog1);        
        arrayList.add(dog2);        
        arrayList.add(dog3);
        System.out.println(arrayList);
    }
}
class Dog{
    String name;
    int age;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public Dog(String name, int age) {
        super();
        this.name = name;
        this.age = age;
    }
    @Override
    public String toString() {
        return "[name=" + name + ", age=" + age + "]";
    }
}

Project 6

public class Week18_1_6 {
//equals 和 ==    ==判断两个东西是否是一个东西（内存地址一样）。  equals() 判断值是否相同
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String s1 = new String("hello");
        String s2 = new String("hello");
        System.out.println(s1==s2);//s1 s2 内存地址肯定不一样  false
        System.out.println(s1.equals(s2));//判断的是值  true
        Student s3 = new Student("21215010", "贾诩", 18);
        Student s4 = new Student("21215010", "贾诩", 18);
        System.out.println(s3==s4);
        System.out.println(s3.equals(s4));//应该在学生类里面重写equals  
    }
}
class Student{
    String number;
    String name;
    int age;
    public Student(String number,String name, int age) {
        this.number=number;
        this.name = name;
        this.age = age;
    }
    public boolean equals(Student s1) {
        return this.number.equals(s1.number) && this.name.equals(s1.name) && this.age==s1.age;
    }
}

开发的时候删除多还是查找多？？？

解释迭代器

取元素