Use and introduction of Optional class for null related processing

package day15_java_class;

import java.util.Optional;

/**
 * Optional类中要进行null相关处理
 * @author asus
 *返回空数据：public static <T> Optional<T> empty();
 *获取数据： public T get();
 *保存数据，但是不容许出现null:public staic <T> Optional <T> of(T value)
 *如果保存数据时存在有null,抛出异常：NullPointerException异常
 *保存数据允许为空：public static <T> Optional <T> ofNullable(T value)
 *空的时候返回其他数据：public T orElse(T other)
 */
interface IMessages{
	public String getContent();
}
class MessageImpl implements IMessages{

	@Override
	public String getContent() {
		// TODO Auto-generated method stub
		return "welcome to !";
		
	}
	
}
class MessageUtil{
	private MessageUtil() {}
	public static Optional <IMessages> getMessage() {
		return Optional.of(new MessageImpl());
	}
	public static void useMessage(IMessages msg) {
		if(msg != null) {
		System.out.println(msg.getContent());
	}else {
		System.out.println("输入有误，不应为空。^ 。");
	}
	}
}
public class java_Optional_class {
public static void main(String[] args) {
	IMessages temp = MessageUtil.getMessage().orElse(new MessageImpl());
	MessageUtil.useMessage(temp);
}
}