Java Tips

1、map.values() 转换成List Collection<String> valueCollection = map.values(); List<String> valueList = new ArrayList<String>(valueCollection);

2、List元素排序

Collections.sort(timeList, new Comparator<Integer>() { @Override public int compare(Integer o1, Integer o2) { return o1.compareTo(o2); } });

3、Velocity VM模版加载相对路径设置

<!-- velocity 配置相关属性如VM加载路径--> <bean class="org.springframework.ui.velocity.VelocityEngineFactoryBean"> <property name="velocityProperties"> <map> <entry key="resource.loader" value="class"/> <entry key="class.resource.loader.class" value="org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader"/> </map> </property> </bean>

4、double保留指定位数

private double truncateFloatNum(double source){ BigDecimal b = new BigDecimal(source); return b.setScale(4, BigDecimal.ROUND_HALF_UP).doubleValue(); }

5、查看crontab message&log

tail -fn 10 /var/log/messages tail -fn 10 /var/log/cron

6、两个整数相除保留指定位小数

private double divideTwoInteger(int divisor, int dividend){ double a = divisor; double b = dividend; if (Double.isInfinite(result) || Double.isNaN(result))             return 0.0; return new BigDecimal(a / b).setScale(3, BigDecimal.ROUND_HALF_UP).doubleValue(); }