List中存储实体类并根据实体类的指定属性去重

场景：

• 如果List中存储的是一些字符串，去重的时候就比较简单，直接使用java中的set集合去重即可。
• 如果List中存储的是一些是实体类，去重的时候，要根据实体类的部分属性去重，可以使用下面的方法。

举例如下：

• 实体类

public class TestBean {
    public String name;
    public String listName;
	public int age;
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getListName() {
        return listName;
    }

    public void setListName(String listName) {
        this.listName = listName;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
    
    @Override
    public String toString() {
        return "TestBean{" +
                "name='" + name + '\'' +
                ", listName='" + listName + '\'' +
                ", age=" + age +
                '}';
    }
}

• 测试类

public class test01 {
    public static void main(String[] args) {
        List<TestBean> list = new ArrayList<>();
        TestBean testBean1 = new TestBean();
        testBean1.setName("a");
        testBean1.setListName("a");
        testBean1.setAge(1);

        TestBean testBean2 = new TestBean();
        testBean2.setName("a");
        testBean2.setListName("a");
        testBean2.setAge(4);

        TestBean testBean3 = new TestBean();
        testBean3.setName("a");
        testBean3.setListName("b");
        testBean3.setAge(1);

        TestBean testBean4 = new TestBean();
        testBean4.setName("a");
        testBean4.setListName("c");
        testBean4.setAge(3);

        TestBean testBean5 = new TestBean();
        testBean5.setName("a");
        testBean5.setListName("d");
        testBean5.setAge(2);

        list.add(testBean1);
        list.add(testBean2);
        list.add(testBean3);
        list.add(testBean4);
        list.add(testBean5);

        System.out.println("原list大小：" + list.size());
        for (TestBean t : list) {
            System.out.println(t);
        }
        List<TestBean> removeDuplicateList = list.stream()
                .collect(Collectors.collectingAndThen(Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(o -> o.getListName() + ";" + o.getName()))), ArrayList::new));
        System.out.println("去重后的list大小：" + removeDuplicateList.size());
        for (TestBean t : removeDuplicateList) {
            System.out.println(t);
        }
        System.out.println("去重后按照年龄倒序后的list=======================");
        removeDuplicateList.sort(Comparator.comparing(TestBean::getAge).reversed());
        for (TestBean t : removeDuplicateList) {
            System.out.println(t);
        }
        System.out.println("去重后按照年龄正序后的list=======================");
        removeDuplicateList.sort(Comparator.comparing(TestBean::getAge));
        for (TestBean t : removeDuplicateList) {
            System.out.println(t);
        }
    }
}

• 运行结果

原list大小：5
TestBean{name='a', listName='a', age=1}
TestBean{name='a', listName='a', age=4}
TestBean{name='a', listName='b', age=1}
TestBean{name='a', listName='c', age=3}
TestBean{name='a', listName='d', age=2}
去重后的list大小：4
TestBean{name='a', listName='a', age=1}
TestBean{name='a', listName='b', age=1}
TestBean{name='a', listName='c', age=3}
TestBean{name='a', listName='d', age=2}
去重后按照年龄倒序后的list=======================
TestBean{name='a', listName='c', age=3}
TestBean{name='a', listName='d', age=2}
TestBean{name='a', listName='a', age=1}
TestBean{name='a', listName='b', age=1}
去重后按照年龄正序后的list=======================
TestBean{name='a', listName='a', age=1}
TestBean{name='a', listName='b', age=1}
TestBean{name='a', listName='d', age=2}
TestBean{name='a', listName='c', age=3}