JAVA,MYSQL - UUID

 https://www.uuidgenerator.net/

留言

發佈留言

此網誌的熱門文章

REMOVE JAVA SDK

  sudo rm -fr /Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin sudo rm -fr /Library/PreferencePanes/JavaControlPanel.prefPane sudo rm -fr ~/Library/Application\ Support/Oracle/Java cd /Library/Java/JavaVirtualMachines rm -fr /usr/local/opt/openjdk@11/libexec/openjdk.jdk sudo rm -rf ****.jdk
閱讀更多

JAVA - JPA

HIBERNATE hibernate.ddl-auto : create : will delete and create new table every startup , so will make data lost create-drop : same as create but will delete and create when session down and up update : create when first time and update every startup keep date validate : check and create/update tables every startp none : do noting JPA GeneratedValue(strategy = GenerationType.XXXXXX) the strategy of primary key TABLE: need to use with @TableGenerator  SEQUENCE: use Sequnce (like a temp table) ony Orcale , PSQL,DB2 support IDENTITY:  control by table(database) ORacle not support AUTO : Default ,control by springboot 在Hibernate中，提供了懒加载功能，当需要的时候才查询具体数据，但是在使用@OneToOne关系时， FetchType.LAZY看起来不会生效。 当你查询一个实体类A，这个实体类A持有另一个实体类B的引用，但是A中并没有记录B的主键，这种情况下，即使有懒加载注解，查询实体A的时候依然会执行两条SQL，分别查询实体类A和B对应的表A和表B。这是由于Hibernate的机制导致，并不是你的使用方式有问题或者存在其他bug。 ———————————————— 版权声明：本文为CSDN博主「_古井心」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。 原文链接：https://blog.csdn.net/u010234516/article/details/103011494
閱讀更多

MAP - Sort with stream

 LEETCODE 1636 Given an array of integers   nums , sort the array in   increasing   order based on the frequency of the values. If multiple values have the same frequency, sort them in   decreasing   order. Return the  sorted array . Example 1: Input: nums = [1,1,2,2,2,3] Output: [3,1,1,2,2,2] Explanation: '3' has a frequency of 1, '1' has a frequency of 2, and '2' has a frequency of 3. Example 2: Input: nums = [2,3,1,3,2] Output: [1,3,3,2,2] Explanation: '2' and '3' both have a frequency of 2, so they are sorted in decreasing order. Example 3: Input: nums = [-1,1,-6,4,5,-6,1,4,1] Output: [5,-1,4,4,-6,-6,1,1,1] #1 class Solution { public int[] frequencySort(int[] nums) { return Arrays.stream(nums) .boxed() // boxing to wapped class .collect(Collectors.toMap(e-> e , e-> 1 , Integer::sum))//?? .entrySet() .stream() .sorted((e1,e2) -> e1.getValue().equals(e...
閱讀更多