Scanner、Random、ArrayList类

早睡。

/**
 * Scanner求输入两数之和
 */
public class ScannerTest {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.println("请输入第一个数字：");
        int i = in.nextInt();
        System.out.println("请输入第二个数字：");
        int j = in.nextInt();
        int a = i+j;
        System.out.println("两数之和为："+a);

    }
}

/**
 * 求输入三个数的最大值
 */
public class ScannerTest02 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.println("请输入第1个数字：");
        int a = in.nextInt();
        System.out.println("请输入第2个数字：");
        int b = in.nextInt();
        System.out.println("请输入第3个数字：");
        int c = in.nextInt();

        int temp=a>b?a:b;
        int max =temp>c?temp:c;
        System.out.println("最大值为:"+max);
    }
}

/**
 * 猜字游戏
 * 随机生成1—100中的一个数字，直至猜对。
 */
public class ScannerTest03 {
    public static void main(String[] args) {
        //创建随机数对象
        Random r = new Random();
        //产生一个1-100的随机数
        int number = r.nextInt(100)+1;
        //创建一个输入对象
        Scanner s = new Scanner(System.in);
        while(true){
            System.out.println("请输入你猜的数字（1-100之间）：");
            //循环输入数字，直至猜对，跳出循环，游戏结束
            int inNumber = s.nextInt();
            if(inNumber>number){
                System.out.println("猜的数大了");
            }else if (inNumber<number){
                System.out.println("猜的数小了");
            }else if(inNumber==number){
                System.out.println("恭喜你猜对了");
                System.out.println(number);
            break;
            }

        }
    }
}

/**
 * 生成3个0—10的随机数
 */
public class RandomTest01 {
    public static void main(String[] args) {
        Random random = new Random();
        for (int i = 0; i <3 ; i++) {
            int r = random.nextInt(10);
            System.out.println("number:"+r);
        }
    }
}

/**
 * 获取1-n的随机数（包括n）
 */
public class RandomTest02 {
    public static void main(String[] args) {
        int number = getNumber(5);
        System.out.println(number);
    }
    public static int getNumber(int n){
        Random r = new Random();
        int i = r.nextInt(n)+1;
        return i;
    }
}

**
 * 生成6个1-33之间的随机数，并添加到集合，并遍历
 */
public class ArrayListTest01 {
    public static void main(String[] args) {
        //创建随机数对象
        Random r = new Random();
        //创建可扩容集合对象ArrayList
        ArrayList<Integer> integers = new ArrayList<>();
        for (int i = 0; i <6 ; i++) {
            //产生1-33之间的随机数
            int number = r.nextInt(33)+1;
            //将随机数添加到集合中
            integers.add(number);
        }
        //遍历集合
        for (int i = 0; i <integers.size() ; i++) {
            System.out.println(integers.get(i));
        }
    }
}

**
 * 自定义四个学生对象，存到集合中，并遍历
 */
public class ArrayListTest02 {
    public static void main(String[] args) {
        ArrayList<Student> list = new ArrayList<>();
        Student s1 = new Student("张三",22);
        Student s2 = new Student("张二",21);
        Student s3 = new Student("张一",20);
        Student s4 = new Student("张四",23);
        list.add(s1);
        list.add(s2);
        list.add(s3);
        list.add(s4);
        //遍历
        Iterator<Student> it = list.iterator();
        while (it.hasNext()){
            Student s = it.next();
            System.out.println(s.getName()+"  "+s.getAge());
        }
        for (int i = 0; i <list.size() ; i++) {
            Student s = list.get(i);
            System.out.println(s.getName()+" "+s.getAge());
        }
    }
}

/**
 * 打印指定格式的集合数据:{aaa@bbb@ccc@ddd}
 */
public class ArrayListTest03 {
    public static void main(String[] args) {
        ArrayList<String> list = new ArrayList<>();
        list.add("aaa");
        list.add("bbb");
        list.add("ccc");
        list.add("ddd");
        System.out.print("{");
        for (int i = 0; i <list.size() ; i++) {
            System.out.print(list.get(i));
            if (i!=list.size()-1){
                System.out.print("@");
            }else{
                System.out.print("}");
            }
        }
    }
}

/**
 * 随机产生n个1-1000的随机数，把所有随机产生的偶数放到一个集合中
 */
public class ArrayListTest04 {
    public static void main(String[] args) {
      getEvenNumber(20);

    }
    public static void getEvenNumber(int n){
        ArrayList<Integer> list = new ArrayList<>();
        Random r = new Random();
        for (int i = 0; i <n ; i++) {
            int number = r.nextInt(1000)+1;
            list.add(number);
        }

        ArrayList<Integer> integers = new ArrayList<>();
        System.out.println("20个随机数是：");
        for (int i = 0; i <list.size() ; i++) {
            Integer a = list.get(i);
            System.out.print(" "+a);

            if (a%2==0){
                integers.add(a);
            }
        }
        System.out.println();
        System.out.println("20个数中的偶数是：");
        for (int i = 0; i <integers.size() ; i++) {
            System.out.print(integers.get(i)+" ");
        }
    }
}