maven

maven local cache

local cache

$Default_user_dir/.m2/repository

reference:
https://maven.apache.org/index.html

maven pom.xml

maven.compiler plugin is used to specifi the jave SDK version,
in my local mac, after mvn init , the default version which is 1.7
which might be too old.

1
2
3
4
5
6

<properties>
  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  <maven.compiler.source>1.8</maven.compiler.source>
  <maven.compiler.target>1.8</maven.compiler.target>
</properties>

User should validate the local java sdk, run ‘java -version’, for example,

1
2
3
4

java -version
openjdk version "14.0.2" 2020-07-14
OpenJDK Runtime Environment (build 14.0.2+12-46)
OpenJDK 64-Bit Server VM (build 14.0.2+12-46, mixed mode, sharing)

#java sdk version is important

for example, java sdk 1.7 only has constructor in priority queue

1

PriorityQueue(int initialCapacity, Comparator<? super E> comparator)

while java sdk1.8 has a new contrustor

1

PriorityQueue(Comparator<? super E> comparator)

java SDK will use a default size when create a new PriorityQueue