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

http://www.javadecompilers.com/

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)

Install Oracle JDK 1.8 in CentOS

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