添加stream操作工具类

hutool-core/src/test/java/cn/hutool/core/util/StreamUtilTest.java

@@ -0,0 +1,179 @@
+package cn.hutool.core.util;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * @author yiming
+ * @date 2020/9/4 13:40
+ */
+public class StreamUtilTest {
+
+    static List<User> userList = Arrays.asList(
+        new User(1L, "A", 3, true, true, true),
+        new User(2L, "B", 4, true, true, false),
+        new User(3L, "C", 5, true, false, true),
+        new User(4L, "E", 6, true, false, false),
+        new User(5L, "D", 7, false, true, true),
+        new User(6L, "F", 7, false, false, true),
+        new User(7L, "G", 8, false, true, false),
+        new User(8L, "H", 8, false, false, false)
+    );
+
+    @Test
+    public void testList() {
+        List<Long> userIds = StreamUtil.list(userList, User::getId);
+        Assert.assertEquals(userIds.size(), userList.size());
+    }
+
+    @Test
+    public void testListFilter() {
+        // 提取管理员用户名称
+        List<String> names = StreamUtil.list(userList, User::getName, x -> Boolean.TRUE.equals(x.isAdmin));
+        Assert.assertEquals(names.size(), 4);
+    }
+
+    @Test
+    public void testToSet() {
+        Set<Integer> ages = StreamUtil.toSet(userList, User::getAge);
+        Assert.assertEquals(ages.size(), 6);
+    }
+
+    @Test
+    public void testToSetFilter() {
+        // 提取大于6的元素
+        Set<Integer> ages = StreamUtil.toSet(userList, User::getAge, x -> x.getAge() > 6);
+        Assert.assertEquals(ages.size(), 2);
+    }
+
+    @Test
+    public void testToMap() {
+        Map<Long, User> userMap = StreamUtil.toMap(userList, User::getId);
+        Assert.assertEquals(userMap.size(), userList.size());
+    }
+
+    @Test
+    public void testToMapValue() {
+        Map<Long, String> userNameMap = StreamUtil.toMap(userList, User::getId, User::getName);
+        Assert.assertEquals(userNameMap.size(), userList.size());
+    }
+
+    @Test
+    public void testToMapFilter() {
+        // 提取年龄>5的用户姓名map
+        Map<Long, String> userNameMap = StreamUtil.toMap(userList, User::getId, User::getName, x -> x.getAge() > 5);
+        Assert.assertEquals(userNameMap.size(), 5);
+    }
+
+    @Test
+    public void testToMapMerge() {
+        // 提取用户姓名map - 自定义map的value覆盖策略
+        User tempUser1 = new User(10L, "X", 10, true, false, false);
+        User tempUser2 = new User(10L, "Y", 10, true, false, false);
+        List<User> users = new ArrayList<>();
+        users.add(tempUser1);
+        users.add(tempUser2);
+        // 若新的value同原value，取原value
+        Map<Long, String> userNameMap = StreamUtil.toMap(users, User::getId, User::getName, (v1, v2) -> v1);
+        Assert.assertEquals(userNameMap.get(10L), "X");
+        // 若新的value同原value，取新value
+        userNameMap = StreamUtil.toMap(users, User::getId, User::getName, (v1, v2) -> v2);
+        Assert.assertEquals(userNameMap.get(10L), "Y");
+    }
+
+    @Test
+    public void groupingBy() {
+        // 按年龄分组
+        Map<Integer, List<User>> ageGroupMap = StreamUtil.groupingBy(userList, User::getAge);
+        Assert.assertEquals(ageGroupMap.size(), 6);
+    }
+
+    /**
+     * 测试bean
+     */
+    public static class User {
+
+        private Long id;
+        private String name;
+        private int age;
+        private boolean isAdmin;
+        private boolean isSuper;
+        private boolean gender;
+
+        public User() {
+        }
+
+        public User(Long id, String name, int age, boolean isAdmin, boolean isSuper, boolean gender) {
+            this.id = id;
+            this.name = name;
+            this.age = age;
+            this.isAdmin = isAdmin;
+            this.isSuper = isSuper;
+            this.gender = gender;
+        }
+
+        public Long getId() {
+            return id;
+        }
+
+        public void setId(Long id) {
+            this.id = id;
+        }
+
+        public String getName() {
+            return name;
+        }
+
+        public void setName(String name) {
+            this.name = name;
+        }
+
+        public int getAge() {
+            return age;
+        }
+
+        public User setAge(int age) {
+            this.age = age;
+            return this;
+        }
+
+        public String testMethod() {
+            return "test for " + this.name;
+        }
+
+        public boolean isAdmin() {
+            return isAdmin;
+        }
+
+        public void setAdmin(boolean isAdmin) {
+            this.isAdmin = isAdmin;
+        }
+
+        public boolean isIsSuper() {
+            return isSuper;
+        }
+
+        public void setIsSuper(boolean isSuper) {
+            this.isSuper = isSuper;
+        }
+
+        public boolean isGender() {
+            return gender;
+        }
+
+        public void setGender(boolean gender) {
+            this.gender = gender;
+        }
+
+        @Override
+        public String toString() {
+            return "User [name=" + name + ", age=" + age + ", isAdmin=" + isAdmin + ", gender=" + gender + "]";
+        }
+    }
+}