fix java build

Author: zzzming

.github/workflows/maven.yml

@@ -11,7 +11,7 @@ on:
       - created 
 
 jobs:
-  build:
+  build java:
     runs-on: ubuntu-latest
     steps:
     - name: Check out code
@@ -25,4 +25,5 @@ jobs:
         java-version: 1.8
 
     - name: Build with Maven
+      cd ./java
       run: mvn -B package --file pom.xml