Java——集合练习题

一、Set

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

public class Demo01 {
    public static void main(String[] args) {
//        实例化
        Set<Integer> set=new HashSet();
        set.add(123);
        set.add(456);
        set.add(178123);
//        遍历
        Iterator iter=set.iterator();
        while (iter.hasNext()){
            Object obj=iter.next();
            int i=Integer.parseInt(obj+"");
            System.out.print(i+"\t");
        }
        System.out.println();
        for (int i:set
             ) {
            System.out.print(i+"\t");
        }
    }
}

二、List

public class Student {
    private int id;
    private String name;
    private int age;
    private String sex;
    private float grade;
    public Student(){}
    public Student(int id,String name,int age,String sex,float grade){
        this.id=id;
        this.name=name;
        this.age=age;
        this.sex=sex;
        this.grade=grade;
    }

    public int getId() {
        return this.id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return this.name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return this.age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getSex() {
        return this.sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public float getGrade() {
        return this.grade;
    }

    public void setGrade(float grade) {
        this.grade = grade;
    }
}

import java.util.ArrayList;
import java.util.List;

public class MyClass {
    private String className;
    public List<Student> student=new ArrayList<Student>();
    public MyClass(){}
    public MyClass(String className){
        this.className=className;
    }

    public String getClassName() {
        return this.className;
    }

    public void setClassName(String className) {
        this.className = className;
    }

    public List<Student> getStudent() {
        return student;
    }

    public void setStudent(List<Student> student) {
        this.student = student;
    }
}

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class Demo05 {
    public static void main(String[] args) {
        List<Myclass> list=new ArrayList<>();
        Myclass mc1=new Myclass("Java一班");
        mc1.myObj.add(new Myobject(1,"张三1",18,"男",88));
        mc1.myObj.add(new Myobject(2,"张三2",20,"女",99));
        mc1.myObj.add(new Myobject(3,"张三3",18,"男",88));
        list.add(mc1);
        Myclass mc2=new Myclass("C++一班");
        mc2.myObj.add(new Myobject(1,"李四1",18,"男",88));
        mc2.myObj.add(new Myobject(2,"李四2",20,"女",99));
        mc2.myObj.add(new Myobject(3,"李四3",18,"男",88));
        list.add(mc2);
        Myclass mc3=new Myclass("C#一班");
        mc3.myObj.add(new Myobject(1,"王五1",18,"男",88));
        mc3.myObj.add(new Myobject(2,"王五2",20,"女",99));
        mc3.myObj.add(new Myobject(3,"王五3",18,"男",88));
        list.add(mc3);
//        System.out.println(list);
        /*System.out.println("迭代器");
        Iterator<Myclass> iter=list.iterator();
        while(iter.hasNext()){
            Myclass mc=iter.next();
            System.out.println(mc.getClassName());
//            System.out.println(mc.myObj);
            Iterator<Myobject> iter1=mc.myObj.iterator();
            while (iter1.hasNext()){
                Myobject mb=iter1.next();
                System.out.println(mb.getId()+"\t"+mb.getName()+"\t"+mb.getAge()+"\t"+mb.getSex()+"\t"+mb.getGrade());
            }
        }*/
        for (Myclass mc:list
             ) {
            System.out.println(mc.getClassName());
            for (Myobject mb:mc.myObj
                 ) {
                System.out.println(mb.getId()+"\t"+mb.getName()+"\t"+mb.getAge()+"\t"+mb.getSex()+"\t"+mb.getGrade());
            }
        }

    }
}

三、Map

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class Demo05 {
    public static void main(String[] args) {
        List<Myclass> list=new ArrayList<>();
        Myclass mc1=new Myclass("Java一班");
        mc1.myObj.add(new Myobject(1,"张三1",18,"男",88));
        mc1.myObj.add(new Myobject(2,"张三2",20,"女",99));
        mc1.myObj.add(new Myobject(3,"张三3",18,"男",88));
        list.add(mc1);
        Myclass mc2=new Myclass("C++一班");
        mc2.myObj.add(new Myobject(1,"李四1",18,"男",88));
        mc2.myObj.add(new Myobject(2,"李四2",20,"女",99));
        mc2.myObj.add(new Myobject(3,"李四3",18,"男",88));
        list.add(mc2);
        Myclass mc3=new Myclass("C#一班");
        mc3.myObj.add(new Myobject(1,"王五1",18,"男",88));
        mc3.myObj.add(new Myobject(2,"王五2",20,"女",99));
        mc3.myObj.add(new Myobject(3,"王五3",18,"男",88));
        list.add(mc3);
//        System.out.println(list);
        /*System.out.println("迭代器");
        Iterator<Myclass> iter=list.iterator();
        while(iter.hasNext()){
            Myclass mc=iter.next();
            System.out.println(mc.getClassName());
//            System.out.println(mc.myObj);
            Iterator<Myobject> iter1=mc.myObj.iterator();
            while (iter1.hasNext()){
                Myobject mb=iter1.next();
                System.out.println(mb.getId()+"\t"+mb.getName()+"\t"+mb.getAge()+"\t"+mb.getSex()+"\t"+mb.getGrade());
            }
        }*/
        for (Myclass mc:list
             ) {
            System.out.println(mc.getClassName());
            for (Myobject mb:mc.myObj
                 ) {
                System.out.println(mb.getId()+"\t"+mb.getName()+"\t"+mb.getAge()+"\t"+mb.getSex()+"\t"+mb.getGrade());
            }
        }

    }
}