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apach software foundatin distribution directory

groovy

2.4.21

2.5.19

3.0.13

4.0.6
reference:

* Groovy Language Documentation

* Groovy Scripting Reference

groovy basics

groovy tips and techniques

* groovy cheatsheet

* Groovy Cookbook

* varargs in Groovy

varargs : Variable Arguments (Varargs) in Java

online compiler

http://www.cheat-sheets.org/saved-copy/rc015-groovy_online.pdf

Syntax

Five Cool Things You Can Do With Groovy Scripts

Java SE Specifications download

The Java Language Specification, Java SE 19 Edition : pdf | html

The Java Language Specification, Java SE 18 Edition : pdf | html

The Java Language Specification, Java SE 17 Edition : pdf | html

The Java Language Specification, Java SE 16 Edition : pdf | html

The Java Language Specification, Java SE 15 Edition : pdf | html

The Java Language Specification, Java SE 14 Edition : pdf | html

The Java Language Specification, Java SE 13 Edition : pdf | html

The Java Language Specification, Java SE 12 Edition : pdf | html

The Java Language Specification, Java SE 11 Edition : pdf | html

[!TIP] Java Tutorial :

Java Exception Handling

Java Tips, How-tos etc

Java JSON Tutorial

Java Logging

Java Performance

Java Regex - Java Regular Expressions

Java Unit Testing

朝花夕拾——Groovy & Grails

basic

Program structure

Customizable Operators

Operator	Method
`a + b`	`a.plus(b)`
`a - b`	`a.minus(b)`
`a * b`	`a.multiply(b)`
`a / b`	`a.div(b)`
`a % b`	`a.mod(b)`
`a++` or `++a`	`a.next()`

assert [ a: true, b: false ]  +  [ a: false ] == [ a: false, b: false ]
assert [ a: true, b: false  ] << [ a: false ] == [ a: false, b: false ]
difference +(plus) and <<(left shift) :

<< is to add into left hand map

+ it constructs a new Map based on the LHS`

Special Operators

Operator	Meaning	Name
`a ? b : c`	`if(a) b else c`	ternary if
`a ?: b`	`a ? a : b`	Elvis
`a.?b`	`( a==null ) ? a : a.b`	null safe
`a(*list)`	`a(list[0], list[1], ...)`	spread
`list*.a()`	`[list[0].a, list[1].a, ...]`	spread-out
`a.&b`	reference to method b in object a as closure	method closure
`a.@field`	direct field access	dot-at

.& : Method pointer operator

def str = 'example of method reference'
def fun = str.&toUpperCase
assert fun() == str.toUpperCase()
println fun()

// result
EXAMPLE OF METHOD REFERENCE

class Person {
  String name
  Integer age
}
def list = [
  new Person( name: 'Bob'   , age: 42 ) ,
  new Person( name: 'Julia' , age: 35 )
]
String describe(Person p) { "$p.name is $p.age" }

def action = this.&describe
def transform( List<Person> elements, Closure action ) {
  elements.inject([]){ result, e ->
    result << action(e)
    result
  }
}

println transform( list, action )
// result
// [Bob is 42, Julia is 35]

elvis operator

if/elseif{if}/else

references:

5.3. Elvis operator

Groovy Goodness: The Elvis Assignment Operator

usage
?: ( existing Elvis operator )
displayName = user.name ? user.name : 'Anonymous'
displayName = user.name ?: 'Anonymous'
?= ( new elvis assignment shorthand )
name = name ?: 'Hydrogen'   // existing Elvis operator
atomicNumber ?= 2           // new Elvis assignment shorthand

condition:

if fruits is 'apple' or 'orange', get pre-defined number 5 ( number = 5 )

if fruits is watermelon, get particular given numbers. number cannot be null

// by using if/elseif{if}/else
Map option = [:]
if ( [ 'apple', 'orange' ].contains(fruits) ) {
  option = [ "${fruits}" : '5' ]
} else if ( [ 'watermelon' ].contains(fruits) ) {
  if (number) {
    option = [ "${fruits}" : number ]
  }
} else {
  println( 'ERROR: number CANNOT be empty while fruits is watermelon. Exit ...' )
}

// by using elvis operator
Map option = ( [ 'apple', 'orange' ].contains(fruits) ) ? [ "${fruits}" : '5' ]
           : ( [ 'watermelon' ].contains(fruits) ) ? ( number )
              ? [ "${fruits}" : number ]
              : println( 'ERROR: number CANNOT be empty while fruits is watermelon. Exit ...' )
           : [:]

example

Closure option = { String fruits, String number = '' ->
    ( [ 'apple', 'orange' ].contains(fruits) ) ? [ (fruits) : '5' ]
    : ( [ 'watermelon' ].contains(fruits) ) ? ( number )
      ? [ (fruits) : number ]
      : println( 'ERROR: number CANNOT be empty while fruits is watermelon. Exit ...' )
    : [:]
}

assert option('apple') == ['apple' : '5']
assert option('watermelon', '100') == [ 'watermelon' : '100' ]

using [ "${fruits}" : '5' ], the class of key is class org.codehaus.groovy.runtime.GStringImpl

using [ (fruits) : '5' ] , the class of key is class java.lang.String

execute shell commands in groovy

reference

101 groovy script - Execute commands

Jenkins Groovy script to execute shell commands

java.lang.Process

gist: Run shell command in groovy

Get STDERR & STDERR

[!TIP] using new StringBuffer() or new StringBuilder()

i.e.:

def stdout = new StringBuffer(), stderr = new StringBuffer()
def proc = "cmd".execute()
proc.waitForProcessOutput( stdout, stderr )
int exitCode = proc.exitValue()
println( (exitCode == 0) ? stdout : "exit with ${exitCode}. error: ${stderr}" )

def stdout = new StringBuilder(), stderr = new StringBuilder()

def proc = "ls /tmp/NoFile".execute()
proc.consumeProcessOutput( stdout, stderr )
proc.waitForOrKill( 1000 )

int exitCode = proc.exitValue()
println( ( exitCode == 0 ) ? stdout : "error with exit code ${exitCode}.\nSTDERR: ${stderr}" )

def stdout = new StringBuilder(), stderr = new StringBuilder()
def proc = 'ls /tmp/NoFile'.execute()
proc.consumeProcesstdoutput( stdout, stderr )
proc.waitForOrKill(1000)
println( stdout ? "out> \n${stdout}" : '' + stderr ? "err> \n${stderr}" : '' )

Show output during the process

using System.out and System.err

def proc = "ls /tmp/NoFile".execute()
proc.waitForProcessOutput( System.out, System.err )
proc.waitForOrKill(1000)

int exitCode = proc.exitValue()
if ( exitCode != 0 ) {
  println "error with exit code ${exitCode}."
}

with environment

def envVars = ["GROOVY_HOME=/fake/path/groovy-3.0.7", "CLASSPATH=.:/fake/path/groovy-3.0.7/lib"]

def proc = './run.sh'.execute( envVars, new File(".") )
proc.waitForProcessOutput( System.out, System.err )
int exitCode = proc.exitValue()

println( (exitCode != 0) ? "exit with ${exitCode}" : '' )

run.sh
```
env
echo ${GROOVY_HOME}
```
result

with system environment

List envVars = System.getenv().collect { k, v -> "${k}=${v}" }

def proc = "./run.sh".execute( envVars, new File(".") )
proc.waitForProcessOutput( System.out, System.err )
int exitCode = proc.exitValue()

println( (exitCode != 0) ? "exit with ${exitCode}" : '' )

with partular path

reference:

groovy execute shell with environment and working dir

def command = "git log -1"
def proc = command.execute( null, new File('/path/to/folder') )
proc.waitFor()

println """
  ${proc.err.text ?: ''}
  ${proc.in.text ?: ''}
  Process exit code: ${proc.exitValue()}
"""

groovyConsole

environment

[!NOTE]

System.setProperty("file.encoding","UTF-8")

font setup for groovyConsole

Groovy console

> setx JAVA_OPT '-Dfile.encoding=UTF-8 -Dsun.jnu.encoding=UTF-8'
> setx GROOVY_OPT '-Dfile.encoding=UTF-8'
> setx JAVA_TOOL_OPTIONS '-Dfile.encoding=UTF-8'

get console details

charset

import java.nio.charset.Charset

System.out.println( String.format("file.encoding: %s", System.getProperty("file.encoding")) );
System.out.println( String.format("defaultCharset: %s", Charset.defaultCharset().name()) );

result

file.encoding: UTF-8
defaultCharset: UTF-8

font

[!NOTE|label:references:]
GROOVY-6303: Add ability to use a different font for the input/output area of Groovy Console
windows : add font/Name into HKEY_CURRENT_USER\SOFTWARE\JavaSoft\Prefs\groovy\console\ui
> REG ADD "HKCU\SOFTWARE\JavaSoft\Prefs\groovy\console\ui" /v "font/Name" /t REG_SZ /d "Monaco" /f
linux : add fontName into ~/.java/.userPrefs/groovy/ui/prefs.xml

macox : add fontName into ~/Library/Preferences/com.apple.java.JavaPreferences.plist
Groovy Goodness: Customize Groovy Console Visual Output

check font

javax.swing.UIManager.getLookAndFeelDefaults()

// or
javax.swing.UIManager.getLookAndFeelDefaults().each {
  println "... ${it.key} : ${it.value}"
}

import java.awt.Font
for (Map.Entry<Object, Object> entry : javax.swing.UIManager.getDefaults().entrySet()) {
    Object key = entry.getKey();
    Object value = javax.swing.UIManager.get(key);
    if (value != null && value instanceof javax.swing.plaf.FontUIResource) {
      println ".. ${key} : ${value}"
    }
}

result

.. FormattedTextField.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. MenuItem.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. InternalFrame.titleFont : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. RadioButton.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. RadioButton.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. OptionPane.buttonFont : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. ToolTip.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. FormattedTextField.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Panel.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. RadioButtonMenuItem.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. OptionPane.messageFont : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. PopupMenu.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. CheckBoxMenuItem.acceleratorFont : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. MenuItem.acceleratorFont : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. CheckBoxMenuItem.acceleratorFont : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. RadioButtonMenuItem.acceleratorFont : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. RadioButtonMenuItem.acceleratorFont : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. TabbedPane.smallFont : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Panel.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. OptionPane.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. EditorPane.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Label.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. ComboBox.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Button.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. MenuBar.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Tree.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Tree.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. ToolBar.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Button.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. ComboBox.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Label.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. EditorPane.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Menu.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. TextArea.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. TextField.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Spinner.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. CheckBoxMenuItem.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Spinner.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. TextField.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. IconButton.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. InternalFrame.titleFont : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. OptionPane.messageFont : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Menu.acceleratorFont : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Menu.acceleratorFont : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. ToolBar.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. TitledBorder.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Menu.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. FileChooser.listFont : javax.swing.plaf.FontUIResource[family=Segoe UI,name=Segoe UI,style=plain,size=12]
.. ToolTip.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. TitledBorder.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. OptionPane.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. MenuBar.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. TextArea.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. OptionPane.buttonFont : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. CheckBoxMenuItem.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. InternalFrame.optionDialogTitleFont : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. InternalFrame.paletteTitleFont : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Table.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. CheckBox.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. List.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. ToggleButton.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. ScrollPane.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. ScrollPane.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. ToggleButton.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. List.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. ColorChooser.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. CheckBox.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. ColorChooser.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Table.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. MenuItem.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. TableHeader.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. TextPane.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Viewport.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. ProgressBar.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. PasswordField.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. TabbedPane.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Slider.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Slider.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. TabbedPane.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. RadioButtonMenuItem.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. PasswordField.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. ProgressBar.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. TableHeader.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. TextPane.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. MenuItem.acceleratorFont : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. Viewport.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]
.. PopupMenu.font : javax.swing.plaf.FontUIResource[family=Dialog,name=Monaco,style=plain,size=14]

modify font

import javax.swing.plaf.FontUIResource
import javax.swing.UIManager
import java.awt.Font

UIManager.put("Panel.font", new FontUIResource(new Font ("Monaco", Font.PLAIN, 16)));

other options

[!NOTE|label:references:]

Swing UIManager Keys

other options

private void setFont(FontUIResource myFont) {
    UIManager.put("CheckBoxMenuItem.acceleratorFont", myFont);
    UIManager.put("Button.font", myFont);
    UIManager.put("ToggleButton.font", myFont);
    UIManager.put("RadioButton.font", myFont);
    UIManager.put("CheckBox.font", myFont);
    UIManager.put("ColorChooser.font", myFont);
    UIManager.put("ComboBox.font", myFont);
    UIManager.put("Label.font", myFont);
    UIManager.put("List.font", myFont);
    UIManager.put("MenuBar.font", myFont);
    UIManager.put("Menu.acceleratorFont", myFont);
    UIManager.put("RadioButtonMenuItem.acceleratorFont", myFont);
    UIManager.put("MenuItem.acceleratorFont", myFont);
    UIManager.put("MenuItem.font", myFont);
    UIManager.put("RadioButtonMenuItem.font", myFont);
    UIManager.put("CheckBoxMenuItem.font", myFont);
    UIManager.put("OptionPane.buttonFont", myFont);
    UIManager.put("OptionPane.messageFont", myFont);
    UIManager.put("Menu.font", myFont);
    UIManager.put("PopupMenu.font", myFont);
    UIManager.put("OptionPane.font", myFont);
    UIManager.put("Panel.font", myFont);
    UIManager.put("ProgressBar.font", myFont);
    UIManager.put("ScrollPane.font", myFont);
    UIManager.put("Viewport.font", myFont);
    UIManager.put("TabbedPane.font", myFont);
    UIManager.put("Slider.font", myFont);
    UIManager.put("Table.font", myFont);
    UIManager.put("TableHeader.font", myFont);
    UIManager.put("TextField.font", myFont);
    UIManager.put("Spinner.font", myFont);
    UIManager.put("PasswordField.font", myFont);
    UIManager.put("TextArea.font", myFont);
    UIManager.put("TextPane.font", myFont);
    UIManager.put("EditorPane.font", myFont);
    UIManager.put("TabbedPane.smallFont", myFont);
    UIManager.put("TitledBorder.font", myFont);
    UIManager.put("ToolBar.font", myFont);
    UIManager.put("ToolTip.font", myFont);
    UIManager.put("Tree.font", myFont);
    UIManager.put("FormattedTextField.font", myFont);
    UIManager.put("IconButton.font", myFont);
    UIManager.put("InternalFrame.optionDialogTitleFont", myFont);
    UIManager.put("InternalFrame.paletteTitleFont", myFont);
    UIManager.put("InternalFrame.titleFont", myFont);
}
setFont(new FontUIResource(new Font("Monaco", Font.PLAIN, 14)));

programming

basic

Program structure

Customizable Operators

Special Operators

elvis operator

if/elseif{if}/else

execute shell commands in groovy

Get STDERR & STDERR

Show output during the process

with environment

with system environment

with partular path

groovyConsole

environment

get console details

font

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