Java Field equals()用法及代碼示例

java.lang.reflect.Field的equals()方法用於比較兩個字段對象。此方法比較兩個字段對象，如果兩個對象相等，則返回true，否則返回false。當且僅當當它們由相同的類聲明並且具有相同的名稱和類型時，才認為這兩個Field對象相等。在調試對象屬性(這實際上是Java中的類的字段)時，此方法非常有用。

用法:

public boolean equals(Object obj)

參數：此方法接受一個參數obj，它是要與該Field對象進行比較的參考對象。

返回值：如果兩個對象相等，則此方法返回true，否則返回false。

以下示例程序旨在說明equals()方法：
示例1:

// Java program to demonstrate the above method 
  
import java.lang.reflect.Field; 
  
public class GFG { 
  
    public static void main(String[] args) 
        throws NoSuchFieldException, 
               SecurityException 
    { 
  
        // get the array of Field objects 
        Field[] fields 
            = User.class.getDeclaredFields(); 
        Field fieldObj 
            = User.class.getField("name"); 
  
        // print element of field array 
        // and compare it with fieldObj 
        for (int i = 0; i < fields.length; i++) { 
  
            // compare the fields with each other 
            boolean isEquals 
                = fields[i].equals(fieldObj); 
            if (isEquals) { 
                System.out.println( 
                    "Field -> ["
                    + fields[i] + "] and"
                    + " FieldObj -> ["
                    + fieldObj 
                    + "] are equal."); 
            } 
            else { 
                System.out.println( 
                    "Field -> ["
                    + fields[i] + "] and"
                    + " FieldObj -> ["
                    + fieldObj 
                    + "] are not equal."); 
            } 
        } 
    } 
} 
  
// User class 
class User { 
  
    public String name; 
    public int age; 
}

輸出：

Field -> [public java.lang.String User.name]
and
FieldObj -> [public java.lang.String User.name]
are equal.

Field -> [public int User.age]
and
FieldObj -> [public java.lang.String User.name]
are not equal.

示例2:

// Java program to demonstrate the above method 
  
import java.lang.reflect.Field; 
  
public class GFG { 
  
    public static void main(String[] args) 
        throws NoSuchFieldException, 
               SecurityException 
    { 
  
        // get the array of Field objects 
        Field[] fields1 
            = Class.class.getDeclaredFields(); 
        Field[] fields2 
            = Class.class.getDeclaredFields(); 
  
        // print element of field array 1 and compare 
        // it with fields array 2 
        for (int i = 0; i < fields1.length; i++) { 
  
            for (int j = 0; j < fields2.length; j++) { 
  
                // compare the fields with each other 
                boolean isEquals 
                    = fields1[i].equals(fields2[j]); 
                if (isEquals) { 
                    System.out.println( 
                        "Field -> ["
                        + fields1[i] + "] and"
                        + " FieldObj -> ["
                        + fields2[j] 
                        + "] are equal."); 
                } 
                else { 
                    System.out.println( 
                        "Field -> ["
                        + fields1[i] + "] and"
                        + " FieldObj -> ["
                        + fields2[j] 
                        + "] are not equal."); 
                } 
            } 
        } 
    } 
} 
  
// Object of Class which contains 
// noOfStudents and studentNames 
class Class { 
  
    public int noOfStudents; 
    public String[] studentNames; 
}

輸出：

Field -> [public int Class.noOfStudents]
and
FieldObj -> [public int Class.noOfStudents]
are equal.

Field -> [public int Class.noOfStudents]
and
FieldObj -> [public java.lang.String[] Class.studentNames]
are not equal.

Field -> [public java.lang.String[] Class.studentNames]
and
FieldObj -> [public int Class.noOfStudents]
are not equal.

Field -> [public java.lang.String[] Class.studentNames]
and
FieldObj -> [public java.lang.String[] Class.studentNames]
are equal.

參考文獻： https://docs.oracle.com/javase/10/docs/api/java/lang/reflect/Field.html#equals(java.lang.Object)

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注：本文由純淨天空篩選整理自AmanSingh2210大神的英文原創作品 Field equals() method in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。