Java编程中常用到的编程思想

public class SumTest{
    public static void main(String[] args) {
        //求1-100(包含1和100)的数字总和
        int sum = 0;
        for (int i = 1; i <= 100; i++) {
            sum += i ;
        }
        System.out.println("sum = " + sum);
    }
}

public class CountTest{
    public static void main(String[] args) {
        //统计1-100之间(包含1和100)的偶数出现的次数
        int count = 0;
        for (int i = 1; i <= 100; i++) {
            if (i%2==0) {
                count ++;
            }
        }
        System.out.println("count = " + count);
    }
}

public class TempTest{
    public static void main(String[] args) {
        //交换变量a和b的值
        int a = 10;
        int b = 20;
        int temp;
        temp = a;
        a = b;
        b = temp;
        System.out.println("a = " + a);
        System.out.println("b = " + b);
    }
}

public class HelloWorld {
    public static void main(String[] args) {
        //数组反转
        //1.定义两个变量
        //2.start表示小索引
        //3.end表示大索引
        //4.小索引和大索引交换
        //5.小索引++,大索引--
        //6.小索引<大索引交换位置
        //7.小索引>=大索引停止交换
        int[] arr = {19, 28, 37, 46, 50};
        int start = 0;
        int end = arr.length-1;
        int temp = 0;
        while(start<end){
            temp = arr[start];
            arr[start]=arr[end];
            arr[end]=temp;
            start++;
            end--;
        }
        System.out.println(Arrays.toString(arr));
    }
}