Lambda Expressions (Method Reference)

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本文通过四个具体案例展示了Java中Lambda表达式的不同用法：静态方法引用、特定对象实例方法引用、任意对象类型实例方法引用及构造器引用，旨在帮助读者深入理解并灵活运用Lambda表达式。

Lambda Expressions

1.Reference to a static method

    @Test(dataProvider = "persons")
    public void testSortPersons2(Person[] persons) {
        Arrays.sort(persons, PersonUtil::compareByAge);
        assertSortedPersons(persons);
    }

2.Reference to an instance method of a particular object

    @Test(dataProvider = "persons")
    public void testSortPersons3(Person[] persons) {
        Arrays.sort(persons, sean::compareByAge);
        assertSortedPersons(persons);
    }

3.Reference to an instance method of an arbitrary object of a particular type

    public void testSortNames() {
        String[] names = { sean.getName(), wanyu.getName(), shaohan.getName(), mohan.getName() };
        Arrays.sort(names, String::compareToIgnoreCase);
        assertEquals(mohan.getName(), names[0]);
        assertEquals(sean.getName(), names[1]);
        assertEquals(shaohan.getName(), names[2]);
        assertEquals(wanyu.getName(), names[3]);
    }

4.Reference to a constructor

    @Test(dataProvider = "persons")
    public void testTransferElements(Person[] persons) {
        Set<Person> newPersons = PersonUtil.transferElements(Arrays.asList(persons), HashSet<Person>::new);
        assertTrue(newPersons.size() == 4);
        assertTrue(newPersons.contains(shaohan));
        assertTrue(newPersons.contains(mohan));
        assertTrue(newPersons.contains(sean));
        assertTrue(newPersons.contains(wanyu));
    }