Java笔记：小作业

女爷i 2021-09-17 04:46 252阅读 0赞

1、编写Java程序，使用for循环打印菱形。

public static void main(String[] args)
    {
    	int height = 17;
    
    	// 上层
    	int lineCount = (height + 1) / 2;
    	for (int line = 1; line <= lineCount; line++)
    	{
    		// 打印空格
    		int blankCount = (lineCount - line) * 2;
    		for (int blank = 1; blank <= blankCount; blank++)
    		{
    			System.out.print(" ");
    		}
    
    		// 打印星符
    		int starCount = line * 2 - 1;
    		for (int star = 1; star <= starCount; star++)
    		{
    			System.out.print("* ");
    		}
    
    		// 换行
    		System.out.println("");
    	}
    
    	// 下层
    	lineCount = (height - 1) / 2;
    	for (int line = lineCount; line >= 1; line--)
    	{
    		// 打印空格
    		int blankCount = (lineCount - line + 1) * 2;
    		for (int blank = 1; blank <= blankCount; blank++)
    		{
    			System.out.print(" ");
    		}
    
    		// 打印星符
    		int starCount = line * 2 - 1;
    		for (int star = 1; star <= starCount; star++)
    		{
    			System.out.print("* ");
    		}
    
    		// 换行
    		System.out.println("");
    	}
    }

2、使用正则表达式来判断字符串是否为合法的手机号码。

String mobileNo = "13588888888";
    String regex = "^[1](([3][0-9])|([4][5,7,9])|([5][^4,6,9])|([6][6])|([7][3,5,6,7,8])|([8][0-9])|([9][8,9]))[0-9]{8}$";
    boolean result = mobileNo.matches(regex);
    System.out.printf("手机号码：%s，校验结果：%b;", mobileNo, result);

3、使用冒泡排序，将数组从小到大排序。

方式一：

int[] arr = { 15, 21, 12, 34, 25, 42, 13, 28 };
    for (int i = 1; i < arr.length; i++)
    {
    	for (int j = 0; j < arr.length - 1; j++)
    	{
    		if (arr[j] > arr[j + 1])
    		{
    			int temp = arr[j];
    			arr[j] = arr[j + 1];
    			arr[j + 1] = temp;
    		}
    	}
    }

方式二：

int[] arr = { 15, 21, 12, 34, 25, 42, 13, 28 };
    for (int i = 0; i < arr.length; i++)
    {
    	for (int j = i + 1; j < arr.length; j++)
    	{
    		if (arr[i] > arr[j])
    		{
    			int temp = arr[i];
    			arr[i] = arr[j];
    			arr[j] = temp;
    		}
    	}
    }