Java编译生成多个.class文件的原理和作用

// Outer.java
public class Outer {
    public class Inner {
        void display() {
            System.out.println("Inner class");
        }
    }
}

public class Outer {
    void method() {
        class LocalInner {
            void show() {
                System.out.println("Local inner");
            }
        }
        new LocalInner().show();
    }
}

public class Outer {
    Runnable r = new Runnable() {
        @Override
        public void run() {
            System.out.println("Anonymous");
        }
    };
}

public class LambdaExample {
    public static void main(String[] args) {
        Runnable r = () -> System.out.println("Lambda");
        r.run();
    }
}

public enum Color {
    RED, GREEN, BLUE;
}

class Parent<T> {
    void set(T t) { /*...*/ }
}

class Child extends Parent<String> {
    @Override
    void set(String s) { /*...*/ }
}

javap -v Outer$Inner.class

javap -p Outer.class | grep synthetic

javac -g:none -XD-printflat -XD-printsource Outer.java

<!-- Maven配置示例 -->
<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.8.1</version>
        </plugin>
    </plugins>
</build>

// 替代匿名类的lambda
Runnable r = () -> System.out.println("Better");

// 替代内部类的静态嵌套类
public static class StaticNested { ... }