Question

我对如何比较两个列表有疑问吗？
这是我的情况。
我有两个ArrayList（nameList<String>和countList<Integer>）。两个列表都可以包含重复值，并且两个列表的大小也相同。
现在，我必须将这两个列表合并为键值对。为此，我创建了一个类型为Person的自定义列表：

public class Person {

    private String name;
    private Integer charCount;

    public Person(String name, Integer charCount) {
        this.name = name;
        this.charCount = charCount;
    }

    public String Name() {
        return name;
    }

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

    public Integer getCharCount() {
        return charCount;
    }

    public void setCharCount(Integer charCount) {
        this.charCount = charCount;
    }
}

List<Person> plist1 = new ArrayList<Person>();
for (int i=0; i < nameList.size(); i++) {
    plist1.add(new Person(nameList.get(i), countList.get(i)));
}

这给了我正确的价值观：
詹姆斯，5
查尔斯（Charles），6
劳埃德（Lloyd），5
查尔斯，6

我已经创建了另一个数据的列表，其要求与上述完全相同，例如plist2。现在，我必须比较这两个列表。也就是说，我必须检查plist1中包含的名称是否也包含在plist2中。

Answer 1

您可以使用自定义比较器对两个列表进行排序（首先按名称字段，然后按charCount字段），然后循环浏览列表，同时检查两个列表中的对应对象是否相同。

这将为您提供两个列表在它们包含的对象集合中是否相等（对象的顺序可能不相同）。例如：

Sub Send_Files() 'Working in Excel 2000-2016 'For Tips see: http://www.rondebruin.nl/win/winmail/Outlook/tips.htm
    Dim OutApp As Object
    Dim OutMail As Object
    Dim sh As Worksheet
    Dim cell As Range
    Dim FileCell As Range
    Dim rng As Range

    With Application
        .EnableEvents = False
        .ScreenUpdating = False
    End With

    Set sh = Sheets("Sheet1")

    Set OutApp = CreateObject("Outlook.Application")

    For Each cell In sh.Columns("B").Cells.SpecialCells(xlCellTypeConstants)

        'Enter the path/file names in the C:Z column in each row
        Set rng = sh.Cells(cell.Row, 1).Range("C1:Z1")

        If cell.Value Like "?*@?*.?*" And _
           Application.WorksheetFunction.CountA(rng) > 0 Then
            Set OutMail = OutApp.CreateItem(0)

            With OutMail
                .to = cell.Value
                .Subject = "Testfile"
                .Body = "Hi " & cell.Offset(0, -1).Value

                For Each FileCell In rng.SpecialCells(xlCellTypeConstants)
                    If Trim(FileCell) <> "" Then
                        If Dir(FileCell.Value) <> "" Then
                            .Attachments.Add FileCell.Value
                        End If
                    End If
                Next FileCell

                .Send  'Or use .Display
            End With

            Set OutMail = Nothing
        End If
    Next cell

    Set OutApp = Nothing
    With Application
        .EnableEvents = True
        .ScreenUpdating = True
    End With 
End Sub

根据上述算法是相等的，但是在以下情况下，它们将不被视为相等，

plist1 --> James,5
           Charles,6
           Lloyd,5
           Charles,6

plist2 --> Lloyd,5
           Charles,6
           James,5
           Charles,6

Answer 2

好，这是您想要做的完整演示，它正在比较各种列表并显示其结果。在Person类中，您需要像我一样实现equals方法，然后仅在for循环中迭代两个列表，并在与list相同的索引处比较两个对象。如果两个列表的大小不同，则可以简单地返回false。检查此代码。

public class Person {

    private String name;
    private Integer charCount;

    public Person(String name, Integer charCount) {
        this.name = name;
        this.charCount = charCount;
    }

    public String getName() {
        return name;
    }

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

    public Integer getCharCount() {
        return charCount;
    }

    public void setCharCount(Integer charCount) {
        this.charCount = charCount;
    }

    public boolean equals(Object o) {
        if (o == null) {
            return false;
        }
        if (o instanceof Person) {
            Person person = (Person) o;
            return person.getName().equals(this.getName())
                    && person.getCharCount().intValue() == this.getCharCount().intValue();
        }
        return false;
    }

    public static void main(String[] args) {
        List<Person> list1 = Arrays.asList(new Person("a1", 1), new Person("a2", 2));
        List<Person> list2 = Arrays.asList(new Person("a1", 1), new Person("a2", 2));
        List<Person> list3 = Arrays.asList(new Person("a1", 1), new Person("a3", 3));
        // list4 content same as list1 but order different
        List<Person> list4 = Arrays.asList(new Person("a2", 2), new Person("a1", 1));

        System.out.println(compareList(list1, list2));
        // prints true as both list have same person objects and same order

        System.out.println(compareList(list1, list3));
        // prints false as both list have differing content

        System.out.println(compareList(list2, list3));
        // prints false as both list have differing content

        System.out.println(compareList(list1, list4));
        // prints false as both list have same content but differing order
    }

    public static boolean compareList(List<Person> list1, List<Person> list2) {
        if (list1.size() != list2.size()) {
            return false;
        }
        for (int i = 0; i < list1.size(); i++) {
            if (!list1.get(i).equals(list2.get(i))) {
                return false;
            }
        }
        return true;
    }

}

比较Java中两个大型自定义列表的对象

2 个答案: