Java零基础入门到精通

1.ArrayList

编程的时候如果要存储多个数据，使用长度固定的数组存储格式，不一定满足我们的需求，更适应不了变化的需求，那么，此时该如何选择呢?
集合

集合类的特点:提供一种存储空间可变的存储模型，存储的数据容量可以发生改变集合类有很多，目前我们先学习一个:ArrayList

2.ArrayList构造方法和添加方法

java">package Base_one.Base_009;import java.util.ArrayList;public class ArrayListDemo1 {public static void main(String[] args) {
//      ArrayList<String> array =  new ArrayList<>();ArrayList<String> array =  new ArrayList<String>();System.out.println(array); //[]System.out.println(array.add("hello"));System.out.println(array);array.add("world");System.out.println(array);array.add(1,"javase");array.add(3,"javaee");System.out.println(array);array.add(5,"sed"); // .IndexOutOfBoundsException 集合索引越界}
}

3.ArrayList 存储字符串并遍历

java">package Base_one.Base_009;import java.util.ArrayList;public class ArrayListTest1 {public static void main(String[] args) {ArrayList<String> arrayList = new ArrayList<>();arrayList.add("a");arrayList.add("b");arrayList.add("c");arrayList.add("e");System.out.println(arrayList);// 遍历for (int i=0; i<arrayList.size();i++){String s = arrayList.get(i);System.out.println(s);}}
}

4. ArrayList 集合常用方法

java">package Base_one.Base_009;import java.util.AbstractList;
import java.util.ArrayList;public class ArrayListDemo2 {public static void main(String[] args) {AbstractList<String> arr = new ArrayList<String>();arr.add("a");arr.add("b");arr.add("c");System.out.println(arr);System.out.println(arr.remove(0));System.out.println(arr.remove("b"));System.out.println(arr);System.out.println(arr.set(0,"e"));System.out.println(arr);System.out.println(arr.get(0));System.out.println(arr.size());}
}

5. 存储学生对象并遍历

java">package Base_one.Base_009;public class Studet {private String name;private int age;public Studet(){}public Studet(String name,int age){this.name = name;this.age = 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;}
}

java">package Base_one.Base_009;import java.util.AbstractList;
import java.util.ArrayList;public class StudentTest {public static void main(String[] args) {// 创建集合对象ArrayList<Studet> array = new ArrayList<Studet>();// 创建学生对象Studet s1 = new Studet("Tom",18);Studet s2 = new Studet("Alo",20);Studet s3 = new Studet("Tina",22);// 添加学生对象到集合中array.add(s1);array.add(s2);array.add(s3);System.out.println(array); // 输出的都是地址了for(int i= 0;i< array.size();i++){Studet s = array.get(i);System.out.println(s.getName()+","+s.getAge());}}
}

6.升级版本

java">package Base_one.Base_009;public class Studentpro {private String name;private String age;public Studentpro() {}public Studentpro(String name, String age) {this.name = name;this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getAge() {return age;}public void setAge(String age) {this.age = age;}
}

java">package Base_one.Base_009;
import java.util.ArrayList;
import java.util.Scanner;public class StudentProTest {public static void main(String[] args) {ArrayList<Studentpro> array = new ArrayList<Studentpro>();Scanner sc = new Scanner(System.in);System.out.println("输入你要添加几个学生对象：");int cout = sc.nextInt();for (int i = 0;i<cout;i++){System.out.println(String.format("第%d个对象",i));addStudentObject(array);}// 遍历输出for (int i = 0;i<array.size();i++){Studentpro s = array.get(i);System.out.println(s.getName()+","+s.getAge());}}// 定义方法 返回值void类型 参数类型为ArrayListpublic static void addStudentObject(ArrayList<Studentpro> array){Scanner sc = new Scanner(System.in);System.out.println("请输入姓名：");String name = sc.nextLine();System.out.println("请输入年龄");String age = sc.nextLine();Studentpro s = new Studentpro();s.setName(name);s.setAge(age);array.add(s);}
}