TreeUtls
java
public class TreeUtil {
/**
* 使用Map合成树
*
* @param menuList 需要合成树的List
* @param pId 对象中的父ID字段,如:Menu:getPid
* @param id 对象中的id字段 ,如：Menu:getId
* @param rootCheck 判断E中为根节点的条件，如：x->x.getPId()==-1L ,
* x->x.getParentId()==null,x->x.getParentMenuId()==0
* @param setSubChildren E中设置下级数据方法，如： Menu::setSubMenus
* @param <T> ID字段类型
* @param <E> 泛型实体对象
* @return
*/
public static <T, E> List<E> makeTree(List<E> menuList, Function<E, T> pId, Function<E, T> id,
Predicate<E> rootCheck, BiConsumer<E, List<E>> setSubChildren) {
// 按原数组顺序构建父级数据Map，使用Optional考虑pId为null
Map<Optional<T>, List<E>> parentMenuMap = menuList.stream().collect(Collectors.groupingBy(
node -> Optional.ofNullable(pId.apply(node)),
LinkedHashMap::new,
Collectors.toList()));
List<E> result = new ArrayList<>();
for (E node : menuList) {
// 添加到下级数据中
setSubChildren.accept(node, parentMenuMap.get(Optional.ofNullable(id.apply(node))));
// 如里是根节点，加入结构
if (rootCheck.test(node)) {
result.add(node);
}
}
return result;
}
/**
* 树中过滤
*
* @param tree 需要过滤的树
* @param predicate 过滤条件
* @param getChildren 获取下级数据方法，如：MenuVo::getSubMenus
* @return List<E> 过滤后的树
* @param <E> 泛型实体对象
*/
public static <E> List<E> filter(List<E> tree, Predicate<E> predicate, Function<E, List<E>> getChildren) {
return tree.stream().filter(item -> {
if (predicate.test(item)) {
List<E> children = getChildren.apply(item);
if (children != null && !children.isEmpty()) {
filter(children, predicate, getChildren);
}
return true;
}
return false;
}).collect(Collectors.toList());
}
/**
* 树中搜索
*
* @param tree
* @param predicate
* @param getSubChildren
* @return 返回搜索到的节点及其父级到根节点
* @param <E>
*/
public static <E> List<E> search(List<E> tree, Predicate<E> predicate, Function<E, List<E>> getSubChildren) {
Iterator<E> iterator = tree.iterator();
while (iterator.hasNext()) {
E item = iterator.next();
List<E> childList = getSubChildren.apply(item);
if (childList != null && !childList.isEmpty()) {
search(childList, predicate, getSubChildren);
}
if (!predicate.test(item) && (childList == null || childList.isEmpty())) {
iterator.remove();
}
}
return tree;
}
}
public class TreeTest {
// 树节点数
public static Integer size = 5000000;
// 树深度
public static Integer deep = 100;
private static List<MenuVo> menuVos = new ArrayList<>();
@BeforeAll
public static void init() {
long currentId = 1;
List<MenuVo> currentLevel = new ArrayList<>();
MenuVo root = new MenuVo(currentId++, 0L, "Root");
menuVos.add(root);
currentLevel.add(root);
for (int level = 1; level < deep && currentId <= size; level++) {
List<MenuVo> nextLevel = new ArrayList<>();
for (MenuVo parent : currentLevel) {
for (int i = 0; i < size / Math.pow(10, level); i++) {
if (currentId > size)
break;
MenuVo child = new MenuVo(currentId++, parent.getId(), String.format("测试name:%s", currentId));
menuVos.add(child);
nextLevel.add(child);
}
}
currentLevel = nextLevel;
}
}
@Test
public void testBigTree() {
List<MenuVo> tree = TreeUtil.makeTree(menuVos, MenuVo::getPId, MenuVo::getId, x -> x.getPId() == 0,
MenuVo::setSubMenus);
System.out.println(tree);
}
}
@AllArgsConstructor
@Data
public class MenuVo {
private Long id;
private Long pId;
private String name;
private List<MenuVo> subMenus;
public MenuVo() {
}
public MenuVo(Long id, Long pId, String name) {
this.id = id;
this.pId = pId;
this.name = name;
}
}DateUtils
java
//根据年月获取第一天
public static Date getFistDayByYearAndMonth(Integer year, Integer month) {
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.MONTH, month - 1);
calendar.set(Calendar.YEAR, year);
calendar.add(Calendar.MONTH, 0);
calendar.set(Calendar.DAY_OF_MONTH, 1);
return calendar.getTime();
}
//根据年月获取其最后一天
public static Date getLastDayByYearAndMonth(Integer year, Integer month) {
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.MONTH, month - 1);
calendar.set(Calendar.YEAR, year);
calendar.add(Calendar.MONTH, 1);
calendar.set(Calendar.DAY_OF_MONTH, 0);
return calendar.getTime();
}
static DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
static DateTimeFormatter dateTimeFormatter2 = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
static ZoneId zoneId = ZoneId.systemDefault();
@Test
public void toLocalDate() {
Date date = new Date();
LocalDateTime localDateTime = date.toInstant().atZone(zoneId).toLocalDateTime();
System.out.println(dateTimeFormatter2.format(localDateTime));
LocalDate localDate = date.toInstant().atZone(zoneId).toLocalDate();
System.out.println(dateTimeFormatter.format(localDate));
}
@Test
public void toDate() {
LocalDateTime localDateTime = LocalDateTime.now();
Date date = Date.from(localDateTime.atZone(zoneId).toInstant());
System.out.println(DateFormatUtils.format(date, "yyyy-MM-dd HH:mm:ss"));
LocalDate localDate = LocalDate.now();
Date date1 = Date.from(localDate.atStartOfDay(zoneId).toInstant());
System.out.println(DateFormatUtils.format(date1, "yyyy-MM-dd"));
}
@Test
public void firstOrLast() {
LocalDate localDate = LocalDate.of(2020, 1, 10);
System.out.println(dateTimeFormatter.format(localDate.with(TemporalAdjusters.firstDayOfMonth())));//当月第一天
System.out.println(dateTimeFormatter.format(localDate.with(TemporalAdjusters.lastDayOfMonth())));//当月最后一天
}
@Test
public void between() {
LocalDate localDate1 = LocalDate.of(2020, 10, 10);
LocalDate localDate2 = LocalDate.of(2020, 10, 12);
System.out.println(localDate2.toEpochDay() - localDate1.toEpochDay());//2天
LocalDateTime localDateTime1 = LocalDateTime.of(2020, 10, 10, 18, 0, 0);
LocalDateTime localDateTime2 = LocalDateTime.of(2020, 10, 10, 21, 0, 0);
System.out.println(
(localDateTime2.atZone(zoneId).toEpochSecond() - localDateTime1.atZone(zoneId).toEpochSecond()) / 60 / 60
);//3小时
}IOUtils
InputStream<--> String
java
@Test
public void stringToInputStream() throws IOException {
InputStream inputStream = new ByteArrayInputStream("hello world".getBytes(StandardCharsets.UTF_8));
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
String collect = bufferedReader.lines().collect(Collectors.joining());
System.out.println(collect);
}路径处理
可以自动处理windows/linux的斜杠反斜杠的问题
Paths.get("/opt/test").normalize()
输出数据到指定文件中
java
//将list中的数据一行一行写到指定文件中
public static <T> void fileWriterList1(String path, List<T> list) {
try {
BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(path), StandardCharsets.UTF_8));
for (T t : list) {
bufferedWriter.write(t.toString());
bufferedWriter.newLine();
bufferedWriter.flush();
}
bufferedWriter.close();
} catch (Exception e) {
e.printStackTrace();
}
}NumberUtils
java
//分转为万元
public static double changeF2WY(Long amount) {
return BigDecimal.valueOf(amount).divide(new BigDecimal(1000000), BigDecimal.ROUND_HALF_UP).doubleValue();
}
//计算百分比
public static String getPercentNumber(BigDecimal a, BigDecimal b) {
return b == null ? "-" :
b.compareTo(new BigDecimal(0)) == 0 ? "-" :
a == null ? "0.00" :
a.multiply(new BigDecimal(100)).divide(b, 2, BigDecimal.ROUND_HALF_UP).toString();
}StringUtils
java
// 1.2.3转为000001000002000003
public static String turnString(String values) {
StringBuilder obj = new StringBuilder();
if (null == values || values.length() == 0) {
return "";
} else {
for (String value : values.split("\\.")) {
int length = value.length();
if (length > 6) {
obj.append(value, 0, 6);
} else {
for (int i = 0; i < 6 - length; i++) {
obj.append("0");
}
obj.append(value);
}
}
}
return obj.toString();
}
// 000001000002000003转为1.2.3
public static String turnStringToDot(String values) {
StringBuilder obj = new StringBuilder();
if (null == values || values.length() < 6 || values.contains("\\.")) {
return values;
} else {
for (int i = 0; i < values.length() / 6; i++) {
String value = values.substring(i * 6, i * 6 + 6);
String res = value.replaceAll("^(0+)", "");
obj.append(res.length() == 0 ? "0." : res + ".");
}
}
return obj.toString();
}java
// 1.2.3转为000001000002000003
public static String turnString(String values) {
StringBuilder obj = new StringBuilder();
if (null == values || values.length() == 0) {
return "";
} else {
for (String value : values.split("\\.")) {
int length = value.length();
if (length > 6) {
obj.append(value, 0, 6);
} else {
for (int i = 0; i < 6 - length; i++) {
obj.append("0");
}
obj.append(value);
}
}
}
return obj.toString();
}
// 000001000002000003转为1.2.3
public static String turnStringToDot(String values) {
StringBuilder obj = new StringBuilder();
if (null == values || values.length() < 6 || values.contains("\\.")) {
return values;
} else {
for (int i = 0; i < values.length() / 6; i++) {
String value = values.substring(i * 6, i * 6 + 6);
String res = value.replaceAll("^(0+)", "");
obj.append(res.length() == 0 ? "0." : res + ".");
}
}
return obj.toString();
}List/Arrays/String
java
@Test
void B() {
// List --> Arrays
List<string> list = new ArrayList<string>(2);
list.add("1");
list.add("2");
String[] arrays = new String[list.size()];
//如果使用toArray的无参方法，返回值是object[],容易出现类型转换异常
arrays = list.toArray(arrays);
// Arrays ---> List
//asList()返回的对象是一个Arrays内部类，没有实现集合的修改方法
list = new ArrayList<>(Arrays.asList(arrays));
// List --> String
//可以使用common.lang中StringUtils中的join方法
String s = StringUtils.join(list, ",");
//或者使用 Java8中的String.join();
String string = String.join(",", arrays);
// String --> List
stringbuilder sb = new stringbuilder("1,2,3,");
sb.deleteCharAt(0);
List list = new ArrayList(Arrays.asList(sb.toString().split(',')));
//使用Arrays.asList构造的list没有重写add，remove方法，其size不可变，
//为了避免使用该list增删改的接口报错，
//使用new ArrayList()将其包起来即可。
//另外的，当asList的构造参数为基础数据类型数组，
//不能被泛型化的数组时，不能正确转list，
//会把整个数组作为一个元素转为list。此时可以使用
int[] intArr = {1, 2, 3};
List<Integer> list = Arrays.stream(intArr).boxed().collect(Collectors.toList());
}