[Guava]——加入约束

public class test11 {//加入约束public static void main(String[] args) {Set<String> set=Sets.newHashSet();Constraint<String> constraint=new Constraint<String>() {//创建约束@Overridepublic String checkElement(String element) {//非空验证Preconditions.checkNotNull(element);//长度验证5-20位的字符串Preconditions.checkArgument(element.length()>=5 && element.length()<=20);return element;}};Set<String> set2=Constraints.constrainedSet(set, constraint);//cs.add(null);//java.lang.NullPointerException//cs.add("aaas");//java.lang.IllegalArgumentExceptionset2.add("bbddsd");for(String str:set2){System.out.println(str);}}}