I've followed below steps:
$ apt-get remove openjdk-6-jre
$ sudo apt-get install openjdk-7-jdk openjdk-7-jre
$ sudo apt-get install openjdk-7-jdk openjdk-7-jre icedtea-7-plugin
$ JAVA_HOME="/usr/lib/jvm/java-7-openjdk-amd64/"
$ source /etc/environment
$ unzip apache-maven-3.3.9-bin.zip
$ mv apache-maven-3.3.9 /opt/
$ export PATH=/opt/apache-maven-3.3.9/bin:$PATH
$ mvn clean package
[WARN] /var/www/html/cg-api-dev-portal/codegen/swagger-codegen/modules/swagger-codegen/src/main/java/config/ConfigParser.java:10: Import statement for 'org.slf4j.Logger' is in the wrong order. Should be in the 'THIRD_PARTY_PACKAGE' group, expecting not assigned imports on this line. [CustomImportOrder]
[WARN] /var/www/html/cg-api-dev-portal/codegen/swagger-codegen/modules/swagger-codegen/src/main/java/config/ConfigParser.java:11: Import statement for 'org.slf4j.LoggerFactory' is in the wrong order. Should be in the 'THIRD_PARTY_PACKAGE' group, expecting not assigned imports on this line. [CustomImportOrder]
[WARN] /var/www/html/cg-api-dev-portal/codegen/swagger-codegen/modules/swagger-codegen/src/main/java/config/ConfigParser.java:17:5: Missing a Javadoc comment. [JavadocMethod]
[WARN] /var/www/html/cg-api-dev-portal/codegen/swagger-codegen/modules/swagger-codegen/src/main/java/config/ConfigParser.java:38:28: Catch parameter name 'e' must match pattern '^[a-z][a-z0-9][a-zA-Z0-9]*$'. [CatchParameterName]
Audit done.
[INFO]
[INFO] --- maven-enforcer-plugin:1.4.1:enforce (enforce-maven) @ swagger-codegen ---
[INFO]
[INFO] --- maven-enforcer-plugin:1.4.1:enforce (enforce-versions) @ swagger-codegen ---
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ swagger-codegen ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 1563 resources
[INFO]
[INFO] --- maven-compiler-plugin:3.5.1:compile (default-compile) @ swagger-codegen ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 147 source files to /var/www/html/cg-api-dev-portal/codegen/swagger-codegen/modules/swagger-codegen/target/classes
[INFO] -------------------------------------------------------------
[ERROR] COMPILATION ERROR :
[INFO] -------------------------------------------------------------
[ERROR] /var/www/html/cg-api-dev-portal/codegen/swagger-codegen/modules/swagger-codegen/src/main/java/io/swagger/codegen/examples/XmlExampleGenerator.java:[17,32] package org.codehaus.plexus.util does not exist
[INFO] 1 error
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO]
[INFO] swagger-codegen-project ............................ SUCCESS [ 3.055 s]
[INFO] swagger-codegen (core library) ..................... FAILURE [ 11.338 s]
[INFO] swagger-codegen (executable) ....................... SKIPPED
[INFO] swagger-codegen (maven-plugin) ..................... SKIPPED
[INFO] swagger-generator .................................. SKIPPED
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 14.927 s
[INFO] Finished at: 2017-08-16T15:04:43+05:00
[INFO] Final Memory: 40M/580M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.5.1:compile (default-compile) on project swagger-codegen: Compilation failure
[ERROR] /var/www/html/cg-api-dev-portal/codegen/swagger-codegen/modules/swagger-codegen/src/main/java/io/swagger/codegen/examples/XmlExampleGenerator.java:[17,32] package org.codehaus.plexus.util does not exist
[ERROR] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR]
[ERROR] After correcting the problems, you can resume the build with the command
[ERROR] mvn <goals> -rf :swagger-codegen