数据类型各种转换

decimal转换为double

select 
       	cast(avg(pm2_5) as decimal(8,2)) as pm2_5,
        cast(avg(co) as decimal(8,2)) as co,
        cast(avg(so2) as decimal(8,2)) as so2,
       	cast(avg(pm10) as decimal(8,2)) as pm10,
       	cast(avg(o3) as decimal(8,2)) as o3,
       	cast(avg(no2) as decimal(8,2)) as no2
		from env_quality
		where date_format(create_time,'%Y-%m')=date_format(now(),'%Y-%m')
		group by date_format(create_time,'%Y-%m')

BigDecimal转换为double
double pm25 = pm25BDu.setScale(2, BigDecimal.ROUND_HALF_UP).doubleValue();

String转换为int

String str = "123";

try {

    int a = Integer.parseInt(str);

} catch (NumberFormatException e) {

    e.printStackTrace();

}

String str = "123";

try {

    int b = Integer.valueOf(str).intValue()

} catch (NumberFormatException e) {

    e.printStackTrace();

}