• basic
  • Program structure
  • Customizable Operators
  • Special Operators
• method and class
  • Named parameters
• elvis operator
  • if/elseif{if}/else
• execute shell commands in groovy
  • Get STDERR & STDERR
  • Show output during the process
  • with environment
• groovyConsole
  • environment
  • get console details
  • font

[!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

basic

Program structure

Customizable Operators

Special Operators

• .& : 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]
  

method and class

[!NOTE]

• Class members
  • Positional parameters
  • Named parameters
• Varargs

Named parameters

def foo ( Map m ) {
  println "${m.name} : ${m.age}"
}

assert foo( name: 'marslo', age: '18' ) == 'marslo : 18'

Mixing named and positional parameters

def foo ( Map m, Integer i ) {
  println "${m.name} : ${m.age} : ${i}"
}

assert foo( name: 'marslo', age: '18', 123 ) == 'marslo : 18 : 123'

elvis operator

if/elseif{if}/else

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

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}" )

or

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

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}"
  }
  

• or

  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)));