We’re still waiting for closures to come to  Java – the saga continues. Until then we’ll need to write the filter boilerplate code  manually. Filter loops often take an input array/collection, match each element with a condition and, if the condition matches, adds the element to another, filtered list. Here’s an example:

List filteredNames = new ArrayList();

for (String name : names) { //names is the original String Collection/array
    if (name.contains("Sam")) {
        filteredNames.add(name);
    }
}

This code is tedious, error-prone and a time-waster. It takes a minute or two or even longer to write without any errors.

You can use Eclipse templates to generate a filter loop in about 20 seconds. If you haven’t worked with templates before, see this post for an overview.

I’ve created a template that produces a List declaration, enhanced for loop, if statement and an add to the filtered list. The list’s type is taken from the nearest array/collection in scope so should be a fairly good match. It even generates import statements for the List and ArrayList.

You can either import the template (recommended; much faster) or create the template manually.

Import the template (recommended)

Download the template below, then import it into Eclipse.

• filter-template.xml
  

Create the template manually

Alternatively, create the template with the following settings. The template code’s a bit tricky because it does a lot.

List<${type:elemType(list)}> ${filteredList} = new ArrayList<${type}>();

for (${type} ${element:newName(type)} : ${list:var(java.util.Collection)}) {
    if (${cursor}) {
        ${filteredList}.add(${element});
    }
}${:import(java.util.List, java.util.ArrayList)}

Check out the overview of variables if you’re unsure of what the code means.

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