Java Field equals()方法及实例

java.lang.reflect .Field 的 equals() 方法是用来比较两个字段对象。这个方法比较两个字段对象，如果两个对象相等则返回真，否则返回假。两个字段对象被认为是相等的，当且仅当它们由同一个类声明，并且具有相同的名称和类型。这个方法在调试对象属性时非常有帮助，这些属性实际上是Java中类的字段。

语法

public boolean equals(Object obj)

参数： 该方法接受一个参数 obj ，它是要与这个字段对象进行比较的参考对象。

返回值： 如果两个对象相等，该方法返回真，否则返回假。

以下程序说明了equals()方法：

程序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;
}

输出:

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.

程序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;
}

输出:

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.

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