java常用工具方法整理（一）

╰+哭是因爲堅強的太久メ 2022-10-28 14:29 197阅读 0赞

package com.zs.utils;
    
    import java.text.ParseException;
    import java.text.SimpleDateFormat;
    import java.util.List;
    import java.util.regex.Matcher;
    import java.util.regex.Pattern;
    public class MyUtil {
    
    	/**
    	 * @Title: listPaging
    	 * @Description: list分页
    	 * @param list
    	 * @param pageNum
    	 * @param pageSize
    	 * @return List<String>
    	 */
    	public List<String> listPaging(List<String> list, Integer pageNum, Integer pageSize) {
    		if (list == null) {
    			return null;
    		}
    		if (list.size() == 0) {
    			return null;
    		}
    		Integer count = list.size(); // 记录总数
    		Integer pageCount = 0; // 页数
    		if (count % pageSize == 0) {
    			pageCount = count / pageSize;
    		} else {
    			pageCount = count / pageSize + 1;
    		}
    
    		int fromIndex = 0; // 开始索引
    		int toIndex = 0; // 结束索引
    
    		if (pageNum != pageCount) {
    			fromIndex = (pageNum - 1) * pageSize;
    			toIndex = fromIndex + pageSize;
    		} else {
    			fromIndex = (pageNum - 1) * pageSize;
    			toIndex = count;
    		}
    		List<String> pageList = list.subList(fromIndex, toIndex);
    		return pageList;
    	}
    
    	/**
    	 * @Title: binarySearch
    	 * @Description: list集合 根据某一字段值 二分查找
    	 * @param arr
    	 * @param findElem
    	 * @return int
    	 */
    	public int binarySearch(String arr[], String findElem) {
    		int low = 0;
    		int high = arr.length - 1;
    		int mid;
    		while (low <= high) {
    			mid = (low + high) / 2;
    			// 如果要查找的元素findElem小于中间位置的元素mid，指向数组的较大端的high索引重新指向中间索引mid的左边（mid-1）
    			if (findElem.compareTo(arr[mid]) < 0) {
    				high = mid - 1;
    			}
    			// 如果要查找的元素findElem大于中间位置的元素mid，指向数组的较小端的low索引重新指向中间索引mid的右边（mid+1）
    			if (findElem.compareTo(arr[mid]) > 0) {
    				low = mid + 1;
    			}
    			if (findElem.compareTo(arr[mid]) == 0) {
    				return mid;
    			}
    		}
    		return -1;
    	}
    
    	public static boolean isValidDate(String str, String strPattern) {
    		boolean convertSuccess = true;
    		SimpleDateFormat format = new SimpleDateFormat(strPattern);
    		try {
    			format.setLenient(false);
    			format.parse(str);
    			/*
    			 * Date day=new Date(); SimpleDateFormat df = new SimpleDateFormat("yyyy");
    			 * String thisYear = df.format(day)+"01"; if (str.compareTo(thisYear) >0) {
    			 * convertSuccess = true; } else { convertSuccess=false; }
    			 */
    		} catch (ParseException e) {
    			// e.printStackTrace();
    			// 如果throw java.text.ParseException或者NullPointerException，就说明格式不对
    			convertSuccess = false;
    		} catch (NullPointerException e) {
    			convertSuccess = false;
    		}
    		return convertSuccess;
    	}
    
    	public static void main(String[] args) {
    		System.out.println(isValidDate("2020/09/01", "yyyy/mm/dd"));
    	}
    
    	public static boolean isNotEmpty(String s) {
    		return null != s && !s.isEmpty();
    	}
    
    	public static boolean isEmpty(String s) {
    		return null == s || s.isEmpty();
    	}
    
    	/**
    	 * @description: 下划线转大驼峰式
    	 * @param: [source]
    	 *             请求参数
    	 * @return: java.lang.String 响应参数
    	 */
    	public static String underlineToBigCamelCase(String source) {
    		String[] strs = source.split("_");
    		StringBuffer stringBuffer = new StringBuffer();
    		for (String s : strs) {
    			stringBuffer.append(upperFirst(s.toLowerCase()));
    		}
    		return String.valueOf(stringBuffer);
    	}
    
    	/**
    	 * @description: 中划线转大驼峰式
    	 * @param: [source]
    	 *             请求参数
    	 * @return: java.lang.String 响应参数
    	 */
    	public static String strikeToBigCamelCase(String source) {
    		String[] strs = source.split("-");
    		StringBuffer stringBuffer = new StringBuffer();
    		for (String s : strs) {
    			stringBuffer.append(upperFirst(s.toLowerCase()));
    		}
    		return String.valueOf(stringBuffer);
    	}
    
    	/**
    	 * @description: 中划线转小驼峰式
    	 * @param: [source]
    	 *             请求参数
    	 * @return: java.lang.String 响应参数
    	 */
    	public static String strikeToLittleCamelCase(String source) {
    		return lowerFirst(strikeToBigCamelCase(source));
    	}
    
    	/**
    	 * @description: 下划线转小驼峰式
    	 * @param: [source]
    	 *             请求参数
    	 * @return: java.lang.String 响应参数
    	 */
    	public static String underlineToLittleCamelCase(String source) {
    		return lowerFirst(underlineToBigCamelCase(source));
    	}
    
    	/**
    	 * @description: 首字母大写
    	 * @param: [source]
    	 *             请求参数
    	 * @return: java.lang.String 响应参数
    	 */
    	public static String upperFirst(String source) {
    		char[] chars = source.toCharArray();
    		chars[0] = 97 <= chars[0] && chars[0] <= 122 ? (char) (chars[0] - 32) : chars[0];
    		return String.valueOf(chars);
    	}
    
    	/**
    	 * @description: 首字母小写
    	 * @param: [source]
    	 *             请求参数
    	 * @return: java.lang.String 响应参数
    	 */
    	public static String lowerFirst(String source) {
    		char[] chars = source.toCharArray();
    		chars[0] = 65 <= chars[0] && chars[0] <= 90 ? (char) (chars[0] + 32) : chars[0];
    		return String.valueOf(chars);
    	}
    
    	/**
    	 * @description: 校验邮箱格式
    	 * @param: [email]
    	 *             请求参数
    	 * @return: boolean 响应参数
    	 */
    	public static boolean validateEmailFormat(String email) {
    		if (StringUtil.isEmpty(email)) {
    			return false;
    		}
    		String regex = "^([a-z0-9A-Z]+[-|.]?)+[a-z0-9A-Z]@([a-z0-9A-Z]+(-[a-z0-9A-Z]+)?\\.)+[a-zA-Z]{2,}$";
    		Pattern pattern = Pattern.compile(regex);
    		Matcher matcher = pattern.matcher(email);
    		return matcher.matches();
    	}
    
    	
    
    }