How to use Lambda expressions in Java language

How to use Lambda expressions in Java language

Java 8 introduces Lambda expressions, which are a new syntax structure that can make the code simple, readable and elegant. Lambda expressions are widely used in Java programming. This article will introduce how to use Lambda expressions in Java.

1. Lambda expression basics

Lambda expression is essentially an anonymous function, which can be passed to a method as a parameter or as a method return value. Lambda expressions have the following basic syntax structure:

(parameter list) -> Expression or statement block

For example:

(int x) -> x 1 // The syntax for one parameter

() -> System.out.println("hello") // The syntax for no parameters

(x, y) -> x y // Grammatical form of multiple parameters

The parameter list in Lambda expression syntax can be empty, but the arrow symbol "->" and the curly braces "{}" must exist. The arrow symbol can be followed by an expression or statement block. If it is an expression, the curly braces can be omitted; if it is a statement block, it must be wrapped in curly braces. Each statement in the statement block needs to end with a semicolon.

The return value type of a Lambda expression can be inferred based on the type behind the expression. If there is no type after the expression, the return value type needs to be used.

2. The use of Lambda expressions

The use of Lambda expressions mainly includes the following points:

1. Use Lambda expressions as parameters to pass to methods

The functional interface newly introduced in Java 8 can accept Lambda expressions as parameters, for example:

interface MyInterface {
void print(String msg);
}

MyInterface obj = (s) -> System.out.println(s);
obj.print("hello lambda");

2. Use Lambda expressions to sort the collection

Lambda expressions can also be used to sort collections, for example:

List strList = Arrays.asList("aaa", "bbb", "ccc");
Collections.sort(strList, (s1, s2) -> s1.length() - s2.length());

3. Use Lambda expression to filter

Lambda expression Formulas can also be used to filter collections, for example:

List strList = Arrays.asList("aaa", "bbb", "ccc");
List result = strList .stream().filter(s -> s.startsWith("a")).collect(Collectors.toList());

4. Use Lambda expressions for thread processing

In Java 8, Lambda expressions can be used to simplify thread processing, for example:

new Thread(() -> {

System.out.println("Thread run");

}).start();

5. Use Lambda expressions to process Optional

Optional is a new feature introduced in Java 8, which can be used to solve the problem of null pointer exceptions. Optional objects can be processed using Lambda expressions, for example:

Optional opt = Optional.of("hello lambda");
opt.ifPresent(s -> System.out. println(s));

3. Advantages of Lambda expression

Lambda expression has the following advantages:

1. The code is highly readable

Lambda expressions can make the code more concise and clear, making it easier for people to understand the code.

2. Improve development efficiency

Using Lambda expressions can avoid writing lengthy codes and improve development efficiency.

3. Support parallel processing

Lambda expressions in Java 8 can support parallel processing, allowing programmers to write efficient code faster.

4. Easy to maintain and debug

Using Lambda expressions can make the code easier to maintain and debug, allowing developers to better locate problems.

4. Summary

Lambda expression is an important feature in Java 8, which can make the code simpler, more readable and elegant. In Java programming, Lambda expressions are widely used and can be used in functional interfaces, collection sorting, collection filtering, thread processing, and Optional processing. Using Lambda expressions can improve development efficiency, improve code readability, support parallel processing, and facilitate maintenance and debugging.

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