IComparable.CompareTo(Object) 方法
定義
重要
部分資訊涉及發行前產品,在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊,不做任何明確或隱含的瑕疵擔保。
將目前的執行個體與相同型別的另一個物件相比較,並傳回整數,這個整數表示目前的執行個體在排序次序中,位於另一個物件之前、之後或相同位置。
public:
int CompareTo(System::Object ^ obj);
public int CompareTo (object obj);
public int CompareTo (object? obj);
abstract member CompareTo : obj -> int
Public Function CompareTo (obj As Object) As Integer
參數
- obj
- Object
與這個執行個體相互比較的物件。
傳回
值,表示所比較之物件的相對順序。 傳回值具有這些意義:
值 | 意義 |
---|---|
小於零 | 這個執行個體在排序次序中會在 obj 之前。
|
零 | 這個執行個體在排序次序中的位置和 obj 相同。
|
大於零 | 這個執行個體在排序順序中會跟在 obj 之後。
|
例外狀況
obj
與這個執行個體的型別不同。
範例
下列範例說明 如何使用 CompareTo 來比較實作 IComparable 的物件與另一個 Temperature
物件。 物件 Temperature
會 CompareTo 實作,只要包裝方法的 Int32.CompareTo 呼叫即可。
using namespace System;
using namespace System::Collections;
public ref class Temperature: public IComparable {
/// <summary>
/// IComparable.CompareTo implementation.
/// </summary>
protected:
// The value holder
Double m_value;
public:
virtual Int32 CompareTo( Object^ obj ) {
if (obj == nullptr) return 1;
if ( obj->GetType() == Temperature::typeid ) {
Temperature^ temp = dynamic_cast<Temperature^>(obj);
return m_value.CompareTo( temp->m_value );
}
throw gcnew ArgumentException( "object is not a Temperature" );
}
property Double Value {
Double get() {
return m_value;
}
void set( Double value ) {
m_value = value;
}
}
property Double Celsius {
Double get() {
return (m_value - 32) / 1.8;
}
void set( Double value ) {
m_value = (value * 1.8) + 32;
}
}
};
int main()
{
ArrayList^ temperatures = gcnew ArrayList;
// Initialize random number generator.
Random^ rnd = gcnew Random;
// Generate 10 temperatures between 0 and 100 randomly.
for (int ctr = 1; ctr <= 10; ctr++)
{
int degrees = rnd->Next(0, 100);
Temperature^ temp = gcnew Temperature;
temp->Value = degrees;
temperatures->Add(temp);
}
// Sort ArrayList.
temperatures->Sort();
for each (Temperature^ temp in temperatures)
Console::WriteLine(temp->Value);
return 0;
}
// The example displays the following output to the console (individual
// values may vary because they are randomly generated):
// 2
// 7
// 16
// 17
// 31
// 37
// 58
// 66
// 72
// 95
using System;
using System.Collections;
public class Temperature : IComparable
{
// The temperature value
protected double temperatureF;
public int CompareTo(object obj) {
if (obj == null) return 1;
Temperature otherTemperature = obj as Temperature;
if (otherTemperature != null)
return this.temperatureF.CompareTo(otherTemperature.temperatureF);
else
throw new ArgumentException("Object is not a Temperature");
}
public double Fahrenheit
{
get
{
return this.temperatureF;
}
set
{
this.temperatureF = value;
}
}
public double Celsius
{
get
{
return (this.temperatureF - 32) * (5.0/9);
}
set
{
this.temperatureF = (value * 9.0/5) + 32;
}
}
}
public class CompareTemperatures
{
public static void Main()
{
ArrayList temperatures = new ArrayList();
// Initialize random number generator.
Random rnd = new Random();
// Generate 10 temperatures between 0 and 100 randomly.
for (int ctr = 1; ctr <= 10; ctr++)
{
int degrees = rnd.Next(0, 100);
Temperature temp = new Temperature();
temp.Fahrenheit = degrees;
temperatures.Add(temp);
}
// Sort ArrayList.
temperatures.Sort();
foreach (Temperature temp in temperatures)
Console.WriteLine(temp.Fahrenheit);
}
}
// The example displays the following output to the console (individual
// values may vary because they are randomly generated):
// 2
// 7
// 16
// 17
// 31
// 37
// 58
// 66
// 72
// 95
open System
open System.Collections
type Temperature() =
// The temperature value
let mutable temperatureF = 0.
interface IComparable with
member _.CompareTo(obj) =
match obj with
| null -> 1
| :? Temperature as other ->
temperatureF.CompareTo other.Fahrenheit
| _ ->
invalidArg (nameof obj) "Object is not a Temperature"
member _.Fahrenheit
with get () =
temperatureF
and set (value) =
temperatureF <- value
member _.Celsius
with get () =
(temperatureF - 32.) * (5. / 9.)
and set (value) =
temperatureF <- (value * 9. / 5.) + 32.
let temperatures = ResizeArray()
// Initialize random number generator.
let rnd = Random()
// Generate 10 temperatures between 0 and 100 randomly.
for _ = 1 to 10 do
let degrees = rnd.Next(0, 100)
let temp = Temperature(Fahrenheit=degrees)
temperatures.Add temp
// Sort ResizeArray.
temperatures.Sort()
for temp in temperatures do
printfn $"{temp.Fahrenheit}"
// The example displays the following output to the console (individual
// values may vary because they are randomly generated):
// 2
// 7
// 16
// 17
// 31
// 37
// 58
// 66
// 72
// 95
Imports System.Collections
Public Class Temperature
Implements IComparable
' The temperature value
Protected temperatureF As Double
Public Overloads Function CompareTo(ByVal obj As Object) As Integer _
Implements IComparable.CompareTo
If obj Is Nothing Then Return 1
Dim otherTemperature As Temperature = TryCast(obj, Temperature)
If otherTemperature IsNot Nothing Then
Return Me.temperatureF.CompareTo(otherTemperature.temperatureF)
Else
Throw New ArgumentException("Object is not a Temperature")
End If
End Function
Public Property Fahrenheit() As Double
Get
Return temperatureF
End Get
Set(ByVal Value As Double)
Me.temperatureF = Value
End Set
End Property
Public Property Celsius() As Double
Get
Return (temperatureF - 32) * (5/9)
End Get
Set(ByVal Value As Double)
Me.temperatureF = (Value * 9/5) + 32
End Set
End Property
End Class
Public Module CompareTemperatures
Public Sub Main()
Dim temperatures As New ArrayList
' Initialize random number generator.
Dim rnd As New Random()
' Generate 10 temperatures between 0 and 100 randomly.
For ctr As Integer = 1 To 10
Dim degrees As Integer = rnd.Next(0, 100)
Dim temp As New Temperature
temp.Fahrenheit = degrees
temperatures.Add(temp)
Next
' Sort ArrayList.
temperatures.Sort()
For Each temp As Temperature In temperatures
Console.WriteLine(temp.Fahrenheit)
Next
End Sub
End Module
' The example displays the following output to the console (individual
' values may vary because they are randomly generated):
' 2
' 7
' 16
' 17
' 31
' 37
' 58
' 66
' 72
' 95
備註
方法 CompareTo 是由可排序或排序其值的型別所實作。 它會由非泛型集合物件的方法自動呼叫,例如 Array.Sort ,以排序陣列的每個成員。 如果自訂類別或結構未實 IComparable 作 ,則無法排序其成員,而且排序作業可以擲回 InvalidOperationException 。
這個方法只是定義,必須由特定類別或實值型別實作,才能生效。 傳回值區段中指定之比較的意義 (「之前」、「發生于與 相同的位置,而 」follows「) 取決於特定實作。
根據定義,任何物件都會比較大於 (或遵循) null
,而兩個 Null 參考會彼此相等。
參數 obj
的類型必須與實作這個介面的類別或實值型別相同, ArgumentException 否則會擲回 。
給實施者的注意事項
對於物件 A、B 和 C,下列條件必須為 true:
A.CompareTo (A)
必須傳回零。
如果 A.CompareTo (B)
傳回零, 則 B.CompareTo (A)
必須傳回零。
如果 A.CompareTo (B)
傳回零,而 B.CompareTo (C)
傳回零, 則 A.CompareTo (C)
必須傳回零。
如果 A.CompareTo (B)
傳回零以外的值, 則 B.CompareTo (A)
必須傳回相反符號的值。
如果A.CompareTo (B)
傳回 x
的值不等於零,而B.CompareTo (C
) 傳回與 相同的符號 x
值 y
,則 A.CompareTo (C)
必須傳回與 和 y
相同的符號 x
值。
給呼叫者的注意事項
CompareTo(Object)使用 方法來判斷類別實例的順序。