day07-04-optional

optional

package day07.java8;

import com.google.common.collect.Lists;
import org.apache.commons.lang3.RandomStringUtils;

import java.util.List;
import java.util.Optional;
import java.util.function.Supplier;
/*
optional 优雅的处理null
 */


public class Demo03 {
    public static void main(String[] args) {
        Integer abc = getString("abc").orElse(0);
        System.out.println("string1 = " + abc);

        List<String> list = Lists.newArrayList("aa","abc","dgf","agvbd");
        long count = list.stream().filter(x -> x.length() > 2).count();


//        list.stream().filter(x->x.length()>1).forEach(System.out::println);

        Optional<String> optional = list.stream()
                .filter(x -> x.length() > 6)
                .findFirst();
        if(optional.isPresent()){
            System.out.println(optional.get());
        }
        String string=optional.orElse("fuck");//optional 如果没有值，提供默认值
        System.out.println(string);

//        String s = optional.orElseGet(new Supplier<String>() {
//            @Override
//            public String get() {
//                return "fuck you";
//            }
//        });
        String s =optional.orElseGet(()-> RandomStringUtils.randomAlphanumeric(8));
        System.out.println("s = ========================" );

    }
    public static Optional<Integer> getString(String str){
        if(str==null){
            return Optional.empty();
        }
        Integer length = str.length();
        return Optional.of(length);
    }

}