<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def build_java_docs(app):
 """build java docs and then move the outdir"""

    java_path = app.builder.srcdir + '/../scala-package'
    java_doc_sources = 'find . -type f -name "*.scala" | egrep \"\.\/core|\.\/infer\" | egrep \"\/javaapi\" | egrep -v \"Suite\"'
    java_doc_classpath = ':'.join([
        '`find native -name "*.jar" | grep "target/lib/" | tr "\\n" ":" `',
        '`find macros -name "*.jar" | tr "\\n" ":" `',
        '`find core -name "*.jar" | tr "\\n" ":" `',
        '`find infer -name "*.jar" | tr "\\n" ":" `'
    ])
    _run_cmd('cd {}; scaladoc `{}` -classpath {} -feature -deprecation'
             .format(java_path, java_doc_sources, java_doc_classpath))
    dest_path = app.builder.outdir + '/api/java/docs'
    _run_cmd('rm -rf ' + dest_path)
    _run_cmd('mkdir -p ' + dest_path)
    javadocs = ['index', 'index.html', 'org', 'lib', 'index.js', 'package.html']
    for doc_file in javadocs:
        _run_cmd('cd ' + java_path + ' && mv -f ' + doc_file + ' ' + dest_path + '; exit 0')