Nolequen :
According to API and implementation separation doc the java-library plugin should be used to declare dependencies as api:
apply plugin: 'java-library'
Is java-library full replacement for java plugin? or there are cases when both of them should be used?
Francisco Mateo :
The java-library is plugin is as it names implies: a plugin for Java libraries. If you are developing a library in Java, then it makes sense to use the java-library plugin.
If you are just developing a plain Java application, then simply use the java plugin as usual.
The java-library plugin applies the java plugin internally: https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/java/org/gradle/api/plugins/JavaLibraryPlugin.java#L38