找出三个数中的最大数和最小数

public class MaxNum {
    public static void main(String[] args)
    {
        int num1 = 13 * 15;
        int num2 = 21 * 7;
        int num3 = 14 *17;
        int max ,min;
        System.out.print("这三个数是："+ num1 + " " + num2 + " " + num3);
        max = num1 >= num2 ? num1:num2;
        max = max >= num3 ? max:num3;
        min = num1 <= num2 ? num1:num2;
        min = min <= num3 ? min:num3;
        System.out.print("最大值是：" + max);
        System.out.print("最小值是：" + min);
    }
}

求1 + 2 + ... + 100的值

public class Sum
{
    public static void main(String[] args)
    {
        //方法1 for循环
        int sum = 0,i = 1;
        for(i = 1;i <= 100;i++)
            sum += i;
        System.out.print("1 + 2  + ... +100 =" + sum);

        //方法2 while循环
        sum = 0;i = 1;
        while(i <= 100)
        {
            sum += i;
            i += 1;
        }
        System.out.print("1 + 2  + ... +100 =" + sum);

        //方法3 do...while循环
        sum = 0;i = 1;
        do
        {
            sum += i;
            i += 1; 
        }
        while(i <= 100);
        System.out.print("1 + 2  + ... +100 =" + sum);
    }
}

求100以内的素数

public class Primes
{
    public static void main(String[] args)
    {
        final int MAX = 100;
        int i,k;
        boolean yes;
        for(k = 2;k < MAX;k++)
        {
            yes = true;
            i = 2;
            while(i <= k-1 && yes)
            {
                if (k % i == 0) 
                    yes = false;
                i++;
            }   
            if (yes) 
                System.out.print(k + " ");
        }
    }
}

计算输出1！，2！... 5！以及它们的和

public class Factorials {
    public static void main(String[] args)
    {
        int i,j;
        long s = 0,k;
        for(i = 1;i <= 5;i++)
        {
            k = 1;
            for(j = 1;j <= i;j++)
            {
                k = k * i;
            }
            System.out.print(i + "!=" +k);
            s = s + k;
        }
        System.out.print("Total sum = " + s);
    }
}

编写程序，实现10的阶乘

public class T10 {
    public static void main(String[] args)
    {
        int sum = 1;
        for(int i = 1;i <= 10;i++)
            sum *= i;
        System.out.print("10的阶乘为" + sum);
    }
}

使用冒泡排序法对数组的元素排序

public class BubbleSort {
    public static void main(String[] args)
    {
        int i,j;
        int intArray[] = {135,-65,70,35,97};
        int len = intArray.length;
        //输出数组排序前的排序
        for(i = 0;i < len;i++)
            System.out.print(intArray[i] + " ");
        System.out.print(" ");
        //排序
        for(i = 0;i < len - 1;i++)
            for(j = i + 1;j < len;j++)
                if(intArray[i]>intArray[j])
                {
                    int t = intArray[i];
                    intArray[i] = intArray[j];
                    intArray[j] = t;
                }
        //输出排序结果
        for(i = 0;i < len;i++)
            System.out.print(intArray[i] + " ");
    }
}

使用数组，编写一个可以输入30个学生数学成绩，并可以统计显示他们的总分，平均分，最低分，最高分的程序。

public class pratice3 {
       public static void main(String[] args){
        int[] scores = new int[3];
        double sum=0;
        double avg=0;
        Scanner  input = new Scanner(System.in);
        System.out.println("请输入30个同学的成绩:");
        for(int i=0;i<scores.length;i++){
        System.out.print("这是第"+(i+1)+"个学生的成绩:");
        scores[i]=input.nextInt();//获取输入的成绩
        }
        int max=scores[0];
        int min=scores[0];
        for(int j=0;j<scores.length;j++){
        if(scores[j]>max){
            max=scores[j];
        }
        if(scores[j]<min){
            min=scores[j];  
        }
        sum+=scores[j];
        }
        avg=sum/3;
        System.out.println("该班的总成绩:"+sum);
        System.out.println("该班的平均成绩:"+avg);
        System.out.println("该班的最低分:"+min);
        System.out.println("该班的最高分:"+max);
     
       }  
    }