Over a million developers have joined DZone.
{{announcement.body}}
{{announcement.title}}

Groovy Goodness: Append Values to Appendable Objects

DZone's Guide to

Groovy Goodness: Append Values to Appendable Objects

· Java Zone
Free Resource

Learn how to troubleshoot and diagnose some of the most common performance issues in Java today. Brought to you in partnership with AppDynamics.

Since Groovy 2.1 we have a couple of extra methods available for objects that implement the java.lang.Appendable interface. A lot of Writer objects implement this interface. The documentation of the Appendable interface mentions: An object to which char sequences and values can be appended.

First the leftShift() method is added. This means we can use the leftShift operator (<<) to append a value. Then we also can use the withFormatter() method. We can pass a closure to this method or a java.util.Locale object and a closure. The closure has a single parameter which is a java.util.Formatter instance. We can use this method to add printf-style formatted strings to an Appendable object. If we pass a Locale object to the method the Formatter is created with the specified Locale to created localized printf-sytle formatted strings.

// Create object that implements the Appendable interface.
final Appendable appendable = new StringWriter()

assert appendable in Appendable


// Use leftShift operator to add to Appendable implementation.
appendable << 'Groovy is Gr8!' << newLine


// Use withFormatter() method.
// Formatter object 
// is passed to closure as parameter.
appendable.withFormatter { formatter ->
    // Simple formatter pattern to reorder the arguments.
    formatter.format(/m r %3$1s %2$1s %1$1s %4$1s%n/, 'k', 'a', 'h', 'i')
}


// Use withFormatter() method and use Locale object
// as extra argument. The Locale is passed on
// to create the Formatter object.
appendable.withFormatter(Locale.US) { formatter ->
    formatter.format("US: " + datePattern, date)
}
// Use different Locale.
appendable.withFormatter(new Locale('nl')) { formatter ->
    formatter.format("Dutch: $datePattern", date)
}


// Check result is as expected:
assert appendable.toString() == '''Groovy is Gr8!
m r h a k i
US: January 27, 2013
Dutch: januari 27, 2013
'''


// Helper getters:

String getNewLine() {
    System.getProperty('line.separator')
}

Date getDate() {
    // Simple date to use in withFormatter() methods.
    Date.parse('yyyy-MM-dd', '2013-01-27')
}

String getDatePattern() {
    // Date pattern for Formatter.
    '%1$tB %1$te, %1$tY%n'
}

Code written with Groovy 2.1


 

Understand the needs and benefits around implementing the right monitoring solution for a growing containerized market. Brought to you in partnership with AppDynamics.

Topics:

Published at DZone with permission of Hubert Klein Ikkink, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

THE DZONE NEWSLETTER

Dev Resources & Solutions Straight to Your Inbox

Thanks for subscribing!

Awesome! Check your inbox to verify your email so you can start receiving the latest in tech news and resources.

X

{{ parent.title || parent.header.title}}

{{ parent.tldr }}

{{ parent.urlSource.name }}