Java--一些小实例

1、请设计一个方法，可以实现获取任意范围内的随机数。

package homeworkTwelve;

import java.util.Scanner;

public class SuiJiShu {
public static void main(String[] args) {
    Scanner sc=new Scanner(System.in);
    System.out.println("请输入一个范围的最大值：");
    int s1=sc.nextInt();
    System.out.println("请输入一个范围的最小值：");
    int s3=sc.nextInt();
    int s2=zuizhongzhi(s1,s3);
    System.out.println(s2);
}

public static int zuizhongzhi(int j,int k){
    int x=(int)((Math.random()*(j-k)+k));
    return x;
}
}

2、集合的嵌套遍历
需求：
我们班有学生，每一个学生是不是一个对象。所以我们可以使用一个集合表示我们班级的学生。ArrayList
但是呢，我们旁边是不是还有班级，每个班级是不是也是一个ArrayList。
而我现在有多个ArrayList。也要用集合存储，怎么办呢?

这是主方法：

package jihe;

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



public class First {
public static void main(String[] args) {
    ArrayList list=new ArrayList();
    ArrayList list1=new ArrayList();
    ArrayList list2=new ArrayList();

    Student s1=new Student(20,"小华");
    Student s2=new Student(22,"小明");
    Student s3=new Student(24,"二狗子");
    Student s4=new Student(21,"李建仁");
    Student s5=new Student(23,"丢疯子");


    Student1 c1=new Student1(20,"陈诺");
    Student1 c2=new Student1(22,"姜泥");
    Student1 c3=new Student1(24,"杨柳");
    Student1 c4=new Student1(25,"梅月");
    Student1 c5=new Student1(23,"代红");

    list1.add(s1);
    list1.add(s2);
    list1.add(s3);
    list1.add(s4);
    list1.add(s5);

    list.add(list1);

    list2.add(c1);
    list2.add(c2);
    list2.add(c3);
    list2.add(c4);
    list2.add(c5);

    list.add(list2);

     Iterator it = list.iterator();
     //班级1
     if (it.hasNext()) {
        System.out.println(it.next());
    }
    //班级2
     if (it.hasNext()) {
        System.out.println(it.next());
    }


}
}

班级一：

package jihe;

public class Student {
private int age;
private String name;
public Student() {
    super();
}
public Student(int age, String name) {
    super();
    this.age = age;
    this.name = name;
}
public int getAge() {
    return age;
}
public void setAge(int age) {
    this.age = age;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
@Override
public String toString() {
    return "Stuent [age=" + age + ", name=" + name + "]";
}

}

班级二：

package jihe;

public class Student1 {
private int age;
private String name;
public Student1() {
    super();
}
public Student1(int age, String name) {
    super();
    this.age = age;
    this.name = name;
}
public int getAge() {
    return age;
}
public void setAge(int age) {
    this.age = age;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
@Override
public String toString() {
    return "Student1 [age=" + age + ", name=" + name + "]";
}

}

3、获取10个1-20之间的随机数，要求不能重复

package suijishutwo;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;



public class SuiJiShuTwo {
public static void main(String[] args) {
    Collection sc=new ArrayList();
    while(sc.size()!=10) {
        int x=(int)(Math.random()*20+1);
        if(!sc.contains(x)){
            sc.add(x);
        }
    }
    Iterator it=sc.iterator();
    while (it.hasNext()) {
        System.out.println(it.next());
    }
}
}

4、使用ArrayList集合存储自定义对象并遍历(三种方式去实现)

package bianli;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;

public class BianLi {
public static void main(String[] args) {
    Collection c=new ArrayList();
    c.add("小明");
    c.add("小华");
    c.add("杨柳");

    Object[] obj=c.toArray();
    for (int i = 0; i < obj.length; i++) {
        System.out.print(obj[i]);
        System.out.print(" ");
    }
    System.out.println("");
    Iterator it=c.iterator();
    while(it.hasNext()){
        System.out.print(it.next());
        System.out.print(" ");
    }
    System.out.println("");
    for (int i = 0; i < c.size(); i++) {
        ArrayList c1=(ArrayList)c;
        System.out.print(c1.get(i));
        System.out.print(" ");
    }
}
}