How are Java anonymous inner classes used in functional programming?

Anonymous inner classes are used in functional programming in Java and allow the creation of disposable objects to implement functional interfaces. It simplifies code, provides flexibility, and promotes code reuse.

Java Anonymous inner classes are used in functional programming

An anonymous inner class is a Java class that does not have an explicit name , and declared directly where it is created. They are often used to create disposable objects, especially when implementing functional interfaces.

Syntax:

new Foo() {
    @Override
    public void someMethod() {
        // 自定义实现
    }
};

Practical case:

Use anonymous inner class to implement Comparator interface, To compare two strings based on their length:

List<String> names = Arrays.asList("John", "Alice", "Bob", "Eve");

// 使用匿名内部类实现 Comparator
Comparator<String> comparator = new Comparator<String>() {
    @Override
    public int compare(String s1, String s2) {
        return s1.length() - s2.length();
    }
};

// 根据长度对名称列表排序
Collections.sort(names, comparator);

// 打印已排序的名称列表
System.out.println(names);

Output:

[Alice, Bob, Eve, John]

Advantages:

• Simplicity: Anonymous inner classes allow for quick creation of disposable objects when needed without having to define a separate class.
• Flexibility: The implementation of the object can be customized as needed.
• Code reuse: Anonymous inner classes can be used to reuse code without creating multiple classes.

Notes:

• Scope: Anonymous inner classes can only be accessed within the code block in which they are created.
• Referencing external variables: If an anonymous inner class needs to reference an external variable, the final modifier must be used to ensure that the variable is immutable in the inner class.

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