Can you show some of an example of using lambda expressions in Java?
Certainly! Lambda expressions are a concise way to represent anonymous functions in Java. They are commonly used in functional interfaces, which are interfaces that have only one abstract method. Here’s an example that demonstrates the usage of lambda expressions in Java:
<span class="hljs-keyword">import</span> java.util.ArrayList;
<span class="hljs-keyword">import</span> java.util.List;
<span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title class_">LambdaExample</span> {
<span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title function_">main</span><span class="hljs-params">(String[] args)</span> {
List<String> names = <span class="hljs-keyword">new</span> <span class="hljs-title class_">ArrayList</span><>();
names.add(<span class="hljs-string">"John"</span>);
names.add(<span class="hljs-string">"Jane"</span>);
names.add(<span class="hljs-string">"Alice"</span>);
names.add(<span class="hljs-string">"Bob"</span>);
<span class="hljs-comment">// Using lambda expression to sort the list of names</span>
names.sort((name1, name2) -> name1.compareTo(name2));
<span class="hljs-comment">// Using lambda expression to print each name in the list</span>
names.forEach(name -> System.out.println(name));
<span class="hljs-comment">// Using lambda expression to filter names starting with "J"</span>
names.stream()
.filter(name -> name.startsWith(<span class="hljs-string">"J"</span>))
.forEach(System.out::println);
}
}
In this example, we have a list of names. We use lambda expressions in three different scenarios:
- Sorting the list: The
sortmethod of theListinterface takes aComparatoras an argument. Instead of creating a separateComparatorimplementation, we pass a lambda expression(name1, name2) -> name1.compareTo(name2)directly to thesortmethod. This lambda expression compares two names using thecompareTomethod and returns the result. - Printing each name: The
forEachmethod of theListinterface takes aConsumeras an argument. Again, instead of creating a separateConsumerimplementation, we pass a lambda expressionname -> System.out.println(name)directly to theforEachmethod. This lambda expression accepts a name as input and prints it usingSystem.out.println. - Filtering names: We use the
streammethod of theListinterface to convert the list into a stream. Then, we chain a series of stream operations. In this case, we use thefilteroperation, which takes aPredicateas an argument. We pass a lambda expressionname -> name.startsWith("J")directly to thefilteroperation. This lambda expression checks if a name starts with the letter “J” and returnstrueorfalseaccordingly. Finally, we use theforEachmethod to print each filtered name.
Lambda expressions provide a concise and expressive way to work with functional interfaces in Java, enabling you to write more compact and readable code.