Java-常用工具方法

一 Json转换

1 输出组装好的json

ObjectMapper mapper = new ObjectMapper();
try {
String requiredJson = mapper.writeValueAsString(query);
System.out.println("---------------");
System.out.println(requiredJson);
System.out.println("---------------");
} catch (JsonProcessingException e) {
e.printStackTrace();
}

2 将对象转换成为字符串

String str = JSON.toJSONString(infoDo);
3 将字符串转换成为对象

InfoDo infoDo = JSON.parseObject(strInfoDo, InfoDo.class);
4 将对象集合转换成为字符串

String users = JSON.toJSONString(users);
5 将字符串转换成为对象集合

List<User> userList = JSON.parseArray(userStr, User.class);

二 字符串处理

1 将rawString从startString开始截取至endString

public static List<String> getOneMatchString(String rawString, String startString, String endString) {
    String tempString = rawString;
    int startPos=0;
    int endPos=0;
    List<String> result = new ArrayList<>();

    startPos=startString.length()+tempString.indexOf(startString);
    while ((startPos-startString.length())!= -1){
        endPos=tempString.indexOf(endString);
        if(endPos>startPos){
            result.add(tempString.substring(startPos,endPos));
        }
        tempString=tempString.substring(endPos+endString.length());
        startPos=startString.length()+tempString.indexOf(startString);
    }
    return result;
}
2 转化为百分比格式字符串

public static String toRate(String n){
    try {
        String rate = String.format("%.2f", (Double.parseDouble(n) * 100)) + "%";
        return rate;
    }catch (Exception e){
        e.printStackTrace();
        return "0.00%";
    }
}
3 保留两位小数
public static String formatTwoNumber(String n){
    try {
        String rate = String.format("%.2f", Double.parseDouble(n));
        return rate;
    }catch (Exception e){
        e.printStackTrace();
        return "0.00";
    }
}

三 mybatis常用语句

1 mybatis新增记录后返回id

<selectKey keyProperty="id" order="AFTER" resultType="java.lang.Integer">
SELECT LAST_INSERT_ID()
</selectKey>

2 模糊匹配

<if test="keyword != null and keyword != ''">
  and message_content like CONCAT('%','${keyword}','%')
</if>

3 日期筛选

<if test="startDate !=null  and startDate!=''">
  and DATE_FORMAT(create_time , '%Y-%m-%d') >= DATE_FORMAT(#{startDate} , '%Y-%m-%d')
</if>
<if test="endDate !=null and endDate!=''">
  and DATE_FORMAT(create_time , '%Y-%m-%d') &lt;= DATE_FORMAT(#{endDate} , '%Y-%m-%d')
</if>

 4 选择结构

<if test="category1 != null and category1 != 0">
  <choose>
    <when test="category2 != null and category2 != 0">
      and ae.category1 = #{category1} and  ae.category2 = #{category2}
    </when>
    <otherwise>
      and ae.category1 = #{category1}
    </otherwise>
  </choose>
</if>

 5 循环结构

   id in

<foreach collection="list" separator="," open="(" close=")" item="item">
  #{item.id}
</foreach>

 四 日期格式化与处理

1 获取昨天的日期 格式:"yyyy-MM-dd"

public static String getYesterday(){
    Date dNow = new Date();
    Calendar calendar = Calendar.getInstance();
    //得到前一天的时间
    calendar.add(Calendar.DAY_OF_MONTH, -1);
     Date dBefore = calendar.getTime();
    SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
    //格式化当前时间
    return  sdf.format(dBefore);
}
2 获取n前的日期 格式："yyyy-MM-dd"

public static String getPastNdays(Integer n){
    Date dNow = new Date();
    Calendar calendar = Calendar.getInstance();
    //得到前n天的时间
    calendar.add(Calendar.DAY_OF_MONTH, n-2*n);
    Date dBefore = calendar.getTime();
    SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
    //格式化当前时间
    return  sdf.format(dBefore);
}
3 得到指定日期n天前的日期 格式："yyyy-MM-dd"

public static String getPastNdays(Date date,Integer n) throws ParseException {
    Calendar calendar = Calendar.getInstance();
    calendar.setTime(date);
    //得到前n天的时间
    calendar.add(Calendar.DAY_OF_MONTH, n-2*n);
    Date dBefore = calendar.getTime();
    SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
    //格式化当前时间
    return  sdf.format(dBefore);
}

public static String getPastNdays(String date,Integer n) {
    Calendar calendar = Calendar.getInstance();
    try {
        calendar.setTime(new SimpleDateFormat("yyyy-MM-dd").parse(date));
    } catch (ParseException e) {
        e.printStackTrace();
    }
    calendar.add(Calendar.DAY_OF_MONTH, n-2*n);
    Date dBefore = calendar.getTime();
    SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
    return  sdf.format(dBefore);
}

4 得到指定日期前一天的日期

public static String getYesterday(Date date){
    Calendar calendar = Calendar.getInstance();
    calendar.setTime(date);
    calendar.add(Calendar.DAY_OF_MONTH, -1);
    Date dBefore = calendar.getTime();
    SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
    return  sdf.format(dBefore);
}

public static String getYesterday(String date){
    Calendar calendar = Calendar.getInstance();
    try {
        calendar.setTime(new SimpleDateFormat("yyyy-MM-dd").parse(date));
    } catch (ParseException e) {
        e.printStackTrace();
    }
    calendar.add(Calendar.DAY_OF_MONTH, -1);
    Date dBefore = calendar.getTime();
    SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
    return  sdf.format(dBefore);
}
5 将短时间格式时间转换为字符串 yyyy-MM-dd

public static String dateToStr(Date dateDate) {
    SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
    String dateString = formatter.format(dateDate);
    return dateString;
}

6 将短时间格式字符串转换为时间 yyyy-MM-dd
 
public static Date strToDate(String strDate) {
    SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
    ParsePosition pos = new ParsePosition(0);
    Date strtodate = formatter.parse(strDate, pos);
    return strtodate;
}

7 将短时间格式字符串转换为时间 yyyy-mm-dd hh:mm:ss
 
public static Date strToDates(String strDate) {
    SimpleDateFormat formatter = new SimpleDateFormat("yyyy-mm-dd hh:mm:ss");
    ParsePosition pos = new ParsePosition(0);
    Date strtodate = formatter.parse(strDate, pos);
    return strtodate;
}
8 日期字符串转换为指定格式的日期

public static Date strToDate(String strDate,String formate) {
    SimpleDateFormat formatter = new SimpleDateFormat(formate);
    ParsePosition pos = new ParsePosition(0);
    Date strtodate = formatter.parse(strDate, pos);
    return strtodate;
}
9 获取当前时间

public static String getNow() {
   Date  date=new Date();
    SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    String datetime = formatter.format(date);
    return datetime;
}

10 获取某段时间内的所有日期
    
    public static List<String> findDates(String begin, String  end) {
        Date dBegin=DateUtils.strToDate(begin);
        Date dEnd=DateUtils.strToDate(end);
        List<String> lDate = new ArrayList();
        lDate.add(begin);
        Calendar calBegin = Calendar.getInstance();
        // 使用给定的 Date 设置此 Calendar 的时间
        calBegin.setTime(dBegin);
        Calendar calEnd = Calendar.getInstance();
        // 使用给定的 Date 设置此 Calendar 的时间
        calEnd.setTime(dEnd);
        // 测试此日期是否在指定日期之后
        while (dEnd.after(calBegin.getTime())) {
            // 根据日历的规则，为给定的日历字段添加或减去指定的时间量
            calBegin.add(Calendar.DAY_OF_MONTH, 1);
            Date time = calBegin.getTime();
            lDate.add(DateUtils.dateToStr(time));
        }
        return lDate;
    }

11 根据日期获取当前是星期几
 
public static Integer getWeekByDate(String date){
    Calendar calendar = Calendar.getInstance();
    Date d = strToDate(date);
    calendar.setTime(d);
    SimpleDateFormat format = new SimpleDateFormat("E");
    String s = format.format(calendar.getTime());
    int n = 0;
    if(s.contains("一")){
        n = 1;
    }else if(s.contains("二")){
        n = 2;
    }else if(s.contains("三")){
        n = 3;
    }else if(s.contains("四")){
        n = 4;
    }else if(s.contains("五")){
        n = 5;
    }else if(s.contains("六")){
        n = 6;
    }else if(s.contains("日")){
        n = 7;
    }
    return n;
}
12 计算从startTime-endTime有多少天
public static int days(String startTime,String endTime){
    int days = 0;
    try {
        Date end = new SimpleDateFormat("yyyy-MM-dd").parse(endTime);
        Date start = new SimpleDateFormat("yyyy-MM-dd").parse(startTime);
        long n = ( (end.getTime()-start.getTime())/(24*60*60*1000) ) + 1;
        days = Integer.parseInt(n+"");
    } catch (ParseException e) {
        e.printStackTrace();
        return days;
    }
    return days;
}

13 获取两个日期之间的每个星期的起始日期
public static List<Map<String,String>> getWeekList (String startTime, String endTime){
    List<Map<String,String>> weeks = new ArrayList<>();
    int sub = days(startTime,endTime);
    if(sub<=7){
        Map<String,String> firstWeek = new HashMap<>();
        firstWeek.put("startTime",startTime);
        firstWeek.put("endTime",endTime);
        weeks.add(firstWeek);
    }else {
        int startWeek = getWeekByDate(startTime);
        int week = 7 - startWeek;
        Map<String,String> firstWeek = new HashMap<>();
        firstWeek.put("startTime",startTime);
        String weekSeven = getDateByAfter(startTime,week);
        firstWeek.put("endTime",weekSeven);
        weeks.add(firstWeek);
        sub = sub - week;
        String sunday = weekSeven;
        while(sub >= 7){
            Map<String,String> weeki = new HashMap<>();
            String start = getDateByAfter(sunday,1);
            weeki.put("startTime",start);
            sunday = getDateByAfter(start,6);
            weeki.put("endTime",sunday);
            weeks.add(weeki);
            sub = sub - 7;
        }
        if(sub != 0){
            Map<String,String> weekEnd = new HashMap<>();
            String start = getDateByAfter(sunday,1);
            weekEnd.put("startTime",start);
            weekEnd.put("endTime",endTime);
            weeks.add(weekEnd);
        }
    }
    return weeks;
}
14 获取两个日期之间的每个月的起始日期
public static List<Map<String,String>> getMonthList(String startTime,String endTime){
    String startMonth = startTime.substring(5,7);
    String endMonth = endTime.substring(5,7);
    List<Map<String,String>> result = new ArrayList<>();
    if(startMonth.equals(endMonth)){
        Map<String,String> onlyMonth = new HashMap<>();
        onlyMonth.put("startTime",startTime);
        onlyMonth.put("endTime",endTime);
        result.add(onlyMonth);
    }else {
        String nextStartTime = startTime;
        do{
            Map<String,String> monthi = new HashMap<>();
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            Calendar lastDate = Calendar.getInstance();
            try {
                lastDate.setTime(sdf.parse(nextStartTime));
            } catch (ParseException e) {
                e.printStackTrace();
            }
            monthi.put("startTime",nextStartTime);
            // 设置为这个月的第 1 天
            lastDate.set(Calendar.DATE, 1);
            lastDate.add(Calendar.MONTH, 1);
            nextStartTime = sdf.format(lastDate.getTime());
            lastDate.add(Calendar.DATE, -1);
            String format = sdf.format(lastDate.getTime());
            monthi.put("endTime",format);
            result.add(monthi);
            startMonth = nextStartTime.substring(5,7);
        }while(!startMonth.equals(endMonth));
        Map<String,String> lastMonth = new HashMap<>();
        String lastMonthStart = endTime.substring(0,8)+"01";
        lastMonth.put("startTime",lastMonthStart);
        lastMonth.put("endTime",endTime);
        result.add(lastMonth);
    }
    return result;
}

15 获取两个日期之间的所有日期
public static List<String> getDays(String startTime, String endTime) {
    List<String> days = new ArrayList<String>();
    DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
    try {
        Date start = dateFormat.parse(startTime);
        Date end = dateFormat.parse(endTime);
        Calendar tempStart = Calendar.getInstance();
        tempStart.setTime(start);
        Calendar tempEnd = Calendar.getInstance();
        tempEnd.setTime(end);
        // 日期加1(包含结束)
        tempEnd.add(Calendar.DATE, +1);
        while (tempStart.before(tempEnd)) {
            days.add(dateFormat.format(tempStart.getTime()));
            tempStart.add(Calendar.DAY_OF_YEAR, 1);
        }
    } catch (ParseException e) {
        e.printStackTrace();
    }
    return days;
}

五 浮点数运算

public class ArithUtils{
    //默认除法运算精度
    private static final int DEF_DIV_SCALE = 10;
    //这个类不能实例化
    private ArithUtils(){
    }
    /**
     * 提供精确的加法运算。
     * @param v1 被加数
     * @param v2 加数
     * @return 两个参数的和
     */
    public static double add(double v1,double v2){
        BigDecimal b1 = new BigDecimal(Double.toString(v1));
        BigDecimal b2 = new BigDecimal(Double.toString(v2));
        return b1.add(b2).doubleValue();
    }
    /**
     * 提供精确的减法运算。
     * @param v1 被减数
     * @param v2 减数
     * @return 两个参数的差
     */
    public static double sub(double v1,double v2){
        BigDecimal b1 = new BigDecimal(Double.toString(v1));
        BigDecimal b2 = new BigDecimal(Double.toString(v2));
        return b1.subtract(b2).doubleValue();
    } 
    /**
     * 提供精确的乘法运算。
     * @param v1 被乘数
     * @param v2 乘数
     * @return 两个参数的积
     */
    public static int mul(double v1,double v2){
        BigDecimal b1 = new BigDecimal(Double.toString(v1));
        BigDecimal b2 = new BigDecimal(Double.toString(v2));
       return b1.multiply(b2).setScale(0,BigDecimal.ROUND_HALF_UP).intValue();
    }
 
    /**
     * 提供（相对）精确的除法运算，当发生除不尽的情况时，精确到
     * 小数点以后10位，以后的数字四舍五入。
     * @param v1 被除数
     * @param v2 除数
     * @return 两个参数的商
     */
    public static double div(double v1,double v2){
        return div(v1,v2,DEF_DIV_SCALE);
    }
 
    /**
     * 提供（相对）精确的除法运算。当发生除不尽的情况时，由scale参数指
     * 定精度，以后的数字四舍五入。
     * @param v1 被除数
     * @param v2 除数
     * @param scale 表示表示需要精确到小数点以后几位。
     * @return 两个参数的商
     */
    public static double div(double v1,double v2,int scale){
        if(scale<0){
            throw new IllegalArgumentException(
                "The scale must be a positive integer or zero");
        }
        if(v2==0){
                    return 0;
        }
        BigDecimal b1 = new BigDecimal(Double.toString(v1));
        BigDecimal b2 = new BigDecimal(Double.toString(v2));
        return b1.divide(b2,scale,BigDecimal.ROUND_HALF_UP).doubleValue();
    }
 
    /**
     * 提供精确的小数位四舍五入处理。
     * @param v 需要四舍五入的数字
     * @param scale 小数点后保留几位
     * @return 四舍五入后的结果
     */
    public static double round(double v,int scale){
        if(scale<0){
            throw new IllegalArgumentException(
                "The scale must be a positive integer or zero");
        }
        BigDecimal b = new BigDecimal(Double.toString(v));
        BigDecimal one = new BigDecimal("1");
        BigDecimal result=b.divide(one,scale,BigDecimal.ROUND_HALF_UP);
        return result.doubleValue();
    }
    
    public static String roundString(double v,int scale){
        if(scale<0){
            throw new IllegalArgumentException(
                "The scale must be a positive integer or zero");
        }
        BigDecimal b = new BigDecimal(Double.toString(v));
        BigDecimal one = new BigDecimal("1");
        return  b.divide(one,scale,BigDecimal.ROUND_HALF_UP).toString();
    }
    
    public static BigDecimal roundBigDecimal(double v,int scale){
        if(scale<0){
            throw new IllegalArgumentException(
                "The scale must be a positive integer or zero");
        }
        BigDecimal b = new BigDecimal(Double.toString(v));
        BigDecimal one = new BigDecimal("1");
        return  b.divide(one,scale,BigDecimal.ROUND_HALF_UP);
       
    }
    /**
     * @Description: 根据type决定向上还是取整，还是四舍五入
     * @author: zw
     */
    public static double round(double v,int scale,int type){
        if(scale<0){
            throw new IllegalArgumentException(
                "The scale must be a positive integer or zero");
        }
        BigDecimal b = new BigDecimal(Double.toString(v));
        BigDecimal one = new BigDecimal("1");
        return b.divide(one,scale,type).doubleValue();
    }
    /**
     * @Description: 对double类型最多保留9位
     * @author: zw
     */
    public static double doubleLen(double v,int len){
       DecimalFormat df   = new DecimalFormat("######0.000000000");
      String format = df.format(v);
      
      //保留位数,本来长度<目标长度，直接返回
      if(format.length()<=len){
         return v;
      }
      String sub=format.substring(0,len+1);
      Double val=Double.parseDouble(sub);
      String[] split = sub.split(".");
      if(split.length>=2){
         int scale=split[1].length();
         val=ArithUtils.round(val, scale);
      }
      return val;
    }

    /**
     * 将获取的小数转换为整数
     */
    public static Long doubleParseLong(String doubleStr){
        Long result = null;
        try {
            result = Double.valueOf(doubleStr).longValue();
            return result;
        }catch (Exception e){
            e.printStackTrace();
            return 0L;
        }
    }
}