Useful Java Tips

Common Java Commands

Java Version

$ java -version

Find java path

$ sudo find / -name java

Compile java code

$ javac <.java file name>

Run java class containing main

$ java -cp <jars separated by colon> <class along with package containing main function>

View classes inside jar

$ jar -tf <.jar file>

Find class in collection of jars

$ for i in /usr/lib/hbase/*.jar; do jar -tvf "$i" | grep -Hsi ImportTsv && echo "$i"; done

Disassemble java class file into attribute and method signatures

$ javap <java .class file>

Generate source code (decompile) from .class or .jar

Display java property values.

$ java -XshowSettings:properties -version

Property settings:

    awt.toolkit = sun.lwawt.macosx.LWCToolkit

    file.encoding = UTF-8

    file.encoding.pkg = sun.io

    file.separator = /

    ftp.nonProxyHosts = local|*.local|169.254/16|*.169.254/16|localhost|*.localhost

    gopherProxySet = false

    http.nonProxyHosts = local|*.local|169.254/16|*.169.254/16|localhost|*.localhost

    java.awt.graphicsenv = sun.awt.CGraphicsEnvironment

    java.awt.printerjob = sun.lwawt.macosx.CPrinterJob

    java.class.path = .

    java.class.version = 52.0

    java.endorsed.dirs = /Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/endorsed

    java.ext.dirs = /Users/abulbasar/Library/Java/Extensions

        /Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/ext

        /Library/Java/Extensions

        /Network/Library/Java/Extensions

        /System/Library/Java/Extensions

        /usr/lib/java

    java.home = /Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre

    java.io.tmpdir = /var/folders/ct/qgv470fj7bq6jyjdw39dngzw0000gn/T/

    java.library.path = /Users/abulbasar/Library/Java/Extensions

        /Library/Java/Extensions

        /Network/Library/Java/Extensions

        /System/Library/Java/Extensions

        /usr/lib/java

    java.runtime.name = Java(TM) SE Runtime Environment

    java.runtime.version = 1.8.0_45-b14

    java.specification.name = Java Platform API Specification

    java.specification.vendor = Oracle Corporation

    java.specification.version = 1.8

    java.vendor = Oracle Corporation

    java.vendor.url = http://java.oracle.com/

    java.vendor.url.bug = http://bugreport.sun.com/bugreport/

    java.version = 1.8.0_45

    java.vm.info = mixed mode

    java.vm.name = Java HotSpot(TM) 64-Bit Server VM

    java.vm.specification.name = Java Virtual Machine Specification

    java.vm.specification.vendor = Oracle Corporation

    java.vm.specification.version = 1.8

    java.vm.vendor = Oracle Corporation

    java.vm.version = 25.45-b02

    line.separator = \n

    os.arch = x86_64

    os.name = Mac OS X

    os.version = 10.11.4

    path.separator = :

    socksNonProxyHosts = local|*.local|169.254/16|*.169.254/16|localhost|*.localhost

    sun.arch.data.model = 64

    sun.boot.class.path = /Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/resources.jar

        /Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/rt.jar

        /Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/sunrsasign.jar

        /Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/jsse.jar

        /Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/jce.jar

        /Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/charsets.jar

        /Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/jfr.jar

        /Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/classes

    sun.boot.library.path = /Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib

    sun.cpu.endian = little

    sun.cpu.isalist =

    sun.io.unicode.encoding = UnicodeBig

    sun.java.launcher = SUN_STANDARD

    sun.jnu.encoding = UTF-8

    sun.management.compiler = HotSpot 64-Bit Tiered Compilers

    sun.os.patch.level = unknown

    user.country = US

    user.country.format = US_POSIX

    user.dir = /Users/abulbasar/workspace/java

    user.home = /Users/abulbasar

    user.language = en

    user.name = abulbasar

    user.timezone =

java version "1.8.0_45"

Java(TM) SE Runtime Environment (build 1.8.0_45-b14)

Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)

Download the rpm for linux 64 bit version (for example jdk-8u101-linux-x64.rpm) from oracle download site.

$ ~/Downloads

$ wget \

--no-check-certificate \

--no-cookies --header "Cookie: oraclelicense=accept-securebackup-cookie" \

http://download.oracle.com/otn-pub/java/jdk/8u112-b15/jdk-8u112-linux-x64.rpm

Install yum install the rpm

$ sudo yum localinstall <rpm name e.g.  jdk-8u101-linux-x64.rpm> -y

After installing, you can delete the rpm file.

Set JAVA_HOME in /etc/profile by adding the following line at the end of the file.

export JAVA_HOME=/usr/java/jdk1.8.0_112

Add Repo

$ sudo wget http://repos.fedorapeople.org/repos/dchen/apache-maven/epel-apache-maven.repo -O /etc/yum.repos.d/epel-apache-maven.repo

Install using yum

$ sudo yum install -y apache-maven

Verify

$ mvn -version

Example pom.xml to

Maven Find Dependency Tree

$ mvn dependency:tree

Maven build

$ mvn clean

$ mvn package

Location of MVN tar

References: