import java.util.ArrayList;
import java.util.List;
public class CollectionDemo {
public static void main(String[] args) {
List<String> myList = new ArrayList<>();
myList.add("Hello");
myList.add("World");
String first = myList.get(0);
for (String item : myList) {
System.out.println(item);
}
boolean hasElement = myList.contains("World");
}
}
import java.util.ArrayList;
import java.util.List;
public class GenericsDemo {
public static void main(String[] args) {
List<T> list = new ArrayList<>();
list.add(new Integer(1));
list.add(new String("Hello"));
}
}
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {
String value() default "";
}
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
public class ReflectionDemo {
public static void main(String[] args) {
try {
Class<MyClass> clazz = MyClass.class;
MyClass obj = clazz.getDeclaredConstructor().newInstance();
Field[] fields = clazz.getDeclaredFields();
for (Field field : fields) {
}
Method[] methods = clazz.getDeclaredMethods();
for (Method method : methods) {
}
Method method = clazz.getMethod("sayHello", String.class);
method.invoke(obj, "World");
} catch (Exception e) {
e.printStackTrace();
}
}
}
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class ConcurrencyDemo {
public static void main(String[] args) {
ExecutorService executorService = Executors.newFixedThreadPool(3);
for (int i = 0; i < 10; i++) {
final int taskNumber = i;
executorService.execute(() -> {
try {
} catch (InterruptedException e) {
e.printStackTrace();
}
});
}
executorService.shutdown();
}
}
