Lambda Expressions

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Runnable r = () -> System.out.println("Hello World");

Supplier<String> c = () -> "Hello World";

// Collection::contains is a simple unary method and its behavior is
// clear from the context. A method reference is preferred here.
appendFilter(goodStrings::contains);

// A lambda expression is easier to understand than just tempMap::put in this case
trackTemperature((time, temp) -> tempMap.put(time, temp));

Expression lambdas are preferred over single-line block lambdas.
Method references should generally be preferred over lambda expressions.
For bound instance method references, or methods with arity greater than one, a lambda expression may be easier to understand and therefore preferred. Especially if the behavior of the method is not clear from the context.
The parameter types should be omitted unless they improve readability.
If a lambda expression stretches over more than a few lines, consider creating a method.

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