取一列
list.stream().map(Book -> Book.getName()).collect(Collectors.toList())去重
List<String> myList = listAll.stream().distinct().collect(Collectors.toList());转字符串
将逗号分隔的字符串转换为List
List<String> list = Arrays.asList(str.split(","));
List<String> list = Arrays.asList(StringUtils.split(str, ","));将list转化为逗号分割的字符串
String str = String.join(",", list);
String str = StringUtils.json(list.toArray(), ","); 将字符串中的字符替换
String newStr = str.replace("需替换的字符", "目标字符");两个list合并成一个list的操作
addAll 添加另一集合里面的元素
add 添加整个集合包括 []
List<String> destList = Collections.synchronizedList(new ArrayList<>(Arrays.asList("foo")));
List<String> newList = Arrays.asList("0", "1", "2", "3", "4", "5");
newList.stream().sequential().collect(Collectors.toCollection(() -> destList));
//newList + destList 的内容
//结果 [foo, 0, 1, 2, 3, 4, 5]
System.out.println(destList);
System.out.println("==========================================");
List<String> listOne = new ArrayList<String>();
listOne.add("333");
listOne.add("666");
listOne.add("999");
List<String> listTwo = new ArrayList<String>();
listTwo.add("A");
listTwo.add("B");
listTwo.add("C");
//addAll 添加另一集合里面的元素
//结果[333, 666, 999, A, B, C]
listOne.addAll(listTwo);
System.out.println(listOne);
//add 添加整个集合包括 []
//结果 [A, B, C, [333, 666, 999, A, B, C]]
listTwo.add(listOne.toString());
System.out.println(listTwo);~~~~
排序
//顺序
list.stream().sorted();
//倒序
list.stream().sorted(Compartor.reverseOrder());
// 其他
list.stream.sorted(Comparator.comparing(Student::getAge).reversed())
// 不使用stream
list.sort(Comparator.comparing(Integer::intValue));
list.sort(Comparator.comparing(Integer::intValue).reversed());
list.sort(Comparator.comparing(Student::getAge));
list.sort(Comparator.comparing(Student::getAge).reversed());
