Java 8: Lambda expressions replace anonymous classes

A lambda is a concise way to implement a functional interface (a single abstract method).

Code

Runnable r = () -> System.out.println("running via lambda");
r.run();

Comparator<String> byLen = (a, b) -> Integer.compare(a.length(), b.length());
var names = new ArrayList<>(List.of("bb", "a", "ccc"));
names.sort(byLen);
System.out.println(names);

Output

running via lambda
[a, bb, ccc]

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Published 2026-07-26