JDK 17 新功能示例代码

以下是一些 JDK 17 新功能的示例代码：

1. Sealed Classes:

public abstract sealed class Shape permits Circle, Square {
    // ...
}

public final class Circle extends Shape {
    // ...
}

public final class Square extends Shape {
    // ...
}

2. Pattern Matching for switch:

public String getDayOfWeek(int day) {
    return switch (day) {
        case 1 -> "Monday";
        case 2 -> "Tuesday";
        case 3 -> "Wednesday";
        case 4 -> "Thursday";
        case 5 -> "Friday";
        case 6, 7 -> "Weekend";
        default -> throw new IllegalArgumentException("Invalid day");
    };
}

3. Strong encapsulation of JDK internals:

import jdk.internal.util.ReflectionUtil;

public class InternalAPIExample {
    public static void main(String[] args) {
        ReflectionUtil.invokeMethod(/* internal API method */);
    }
}

4. Foreign Function & Memory API:

import jdk.incubator.foreign.MemorySegment;
import jdk.incubator.foreign.ResourceScope;

public class MemoryExample {
    public static void main(String[] args) {
        try (ResourceScope scope = ResourceScope.newConfinedScope()) {
            MemorySegment segment = MemorySegment.allocateNative(1024, scope);
            // ...
        }
    }
}

这些示例代码展示了 JDK 17 中一些新功能的用法。请注意，某些示例可能需要引入特定的包或模块。确保你的项目配置正确以使用这些功能。