List<String> words ， java 1.8 及以上用lambda表达式
1.
Collections.sort(words,new Comparator<String>(){
public int compare(){
return Integer.compare(s1.length(),s2.length)
}
})
2.collections.sort(words,
(S1,S2) -> Integer.compare(s1.length，s2.length)
)
3.Collections.sort(woeds,compring(String::length));
4.words.sort(compring(String::length))