1. Java 自带工具方法
System.out.println(Objects.equals("a", "a"));
List<String> list = Arrays.asList("a", "b", "c");
String join1 = list.stream().collect(Collectors.joining(","));
System.out.println(join1);
String join2 = String.join(",");
System.out.println(join2);
List<String> list1 = new ArrayList<>();
list1.add("a");
list1.add("b");
list1.add("c");
List<String> list2 = new ArrayList<>();
list2.add("a");
list2.add("b");
list2.add("d");
list1.retainAll(list2);
System.out.println(list1);
2. Apache commons 工具类
2.1. implementation ‘org.apache.commons:commons-lang3:3.12.0’
String str = "";
System.out.println(StringUtils.isEmpty(str));
System.out.println(StringUtils.isNotEmpty(str));
System.out.println(StringUtils.isBlank(str));
System.out.println(StringUtils.isNoneBlank(str));
String str2 = "abc";
System.out.println(StringUtils.capitalize(str2));
System.out.println(StringUtils.repeat(str2, 2));
System.out.println(DateFormatUtils.format(new Date(), "yyyy-MM-dd HH:mm:ss"));
System.out.println(DateUtils.parseDate("2021-07-01 12:12:12", "yyyy-MM-dd HH:mm:ss"));
System.out.println(DateUtils.addHours(new Date(), 1));
ImmutablePair<Integer, String> pair = ImmutablePair.of(1, "test");
System.out.println(pair.getLeft() + " : " + pair.getRight());
ImmutableTriple<Integer, Long, String> triple = ImmutableTriple.of(1, 2L, "test");
System.out.println(triple.getLeft() + " : " + triple.getMiddle() + " : " + triple.getRight());
2.2. implementation ‘org.apache.commons:commons-collections4:4.4’
List<String> list1 = new ArrayList<>();
list1.add("a");
list1.add("b");
list1.add("c");
List<String> list2 = new ArrayList<>();
list2.add("a");
list2.add("c");
list2.add("d");
System.out.println(CollectionUtils.isEmpty(list1));
System.out.println(CollectionUtils.isNotEmpty(list1));
Collection<String> collection1 = CollectionUtils.retainAll(list1, list2);
System.out.println(collection1);
Collection<String> collection2 = CollectionUtils.union(list1, list2);
System.out.println(collection2);
Collection<String> collection3 = CollectionUtils.subtract(list1, list2);
System.out.println(collection3);
3. C
4.