Java Java.util.Arrays.deepEquals()用法及代码示例

Arrays.deepEquals()用于检查一维数组或多维数组的两个数组是否相等。它可以比较两个嵌套数组(即多维数组)，而不管其尺寸如何。

如果两个数组引用都为null，或者两个数组引用都引用了包含相同数量元素的数组，并且两个数组中所有对应的元素对都非常相等，则认为它们是完全相等的。
如果满足以下任一条件，则两个可能为null的元素e1和e2完全相等：
- e1和e2都是对象引用类型的数组，并且Arrays.deepEquals(e1，e2)将返回true
- e1和e2是相同原始类型的数组，并且Arrays.equals(e1，e2)的适当重载将返回true。
- e1 == e2
- e1.equals(e2)将返回true。
请注意，此定义允许在任何深度使用null元素。
它是数组类的一种方法

用法:

public static boolean deepEquals(Object[] o1, Object[] o2)

o1 = First Array to test for Equality
o2 = Second Array to test for Equality

Returns true if two array are equal

// Java program to demonstrate working of deepEquals. 
import java.util.Arrays; 
public class GFG { 
public static void main(String[] args) 
    { 
        int a1[][] = { { 10, 20 }, 
                       { 40, 50 }, 
                       { 60, 70 } }; 
  
        int a2[][] = { { 30, 20 }, 
                       { 10, 0 }, 
                       { 60, 80 } }; 
  
        int a3[][] = { { 10, 20 }, 
                       { 40, 50 }, 
                       { 60, 70 } }; 
        System.out.println("Check if a1 is equal to a2:"
                           + Arrays.deepEquals(a1, a2)); 
  
        System.out.println("Check if a2 is equal to a3:"
                           + Arrays.deepEquals(a2, a3)); 
  
        System.out.println("Check if a1 is equal to a3:"
                           + Arrays.deepEquals(a1, a3)); 
    } 
}

输出：

Check if a1 is equal to a2:false
Check if a2 is equal to a3:false
Check if a1 is equal to a3:true

我们甚至可以使用deepEquals()来测试用户定义类的Object数组的相等性。请参考下面的例子
我们应该重写equals方法，以在用户定义的类中定义不同参数的相等性。

// Java program to demonstrate working of deepEquals 
// for arrays of user defined obj. 
import java.util.Arrays; 
public class GFG { 
public static class Employee { 
  
        int Eid; 
        String Ename; 
  
    public Employee(int Eid, String Ename) 
        { 
            this.Eid = Eid; 
            this.Ename = Ename; 
        } 
  
        // Overriding the equals() 
    public boolean equals(Object obj) 
        { 
  
            // type casting obj to Employee 
            Employee s = (Employee)obj; 
            return (this.Eid == s.Eid && this.Ename.equals(s.Ename)); 
        } 
    } public static void main(String args[]) 
    { 
        // Creating an array of objects of user defined class. 
        Employee e1[][] = { { new Employee(10, "Geek1"), 
                              new Employee(11, "Geek2") }, 
                            { new Employee(12, "Geek3"), 
                              new Employee(13, "Geek4") } }; 
  
        Employee e2[][] = { { new Employee(10, "Geek1"), 
                              new Employee(11, "Geek2") }, 
                            { new Employee(12, "Geek3"), 
                              new Employee(13, "Geek4") } }; 
  
        Employee e3[][] = { { new Employee(12, "Geek2"), 
                              new Employee(25, "Geek4") }, 
                            { new Employee(15, "Geek3"), 
                              new Employee(30, "Geek1") } }; 
  
        System.out.println("Check if e1 is equal to e2:"
                           + Arrays.deepEquals(e1, e2)); 
  
        System.out.println("Check if e2 is equal to e3:"
                           + Arrays.deepEquals(e2, e3)); 
  
        System.out.println("Check if a1 is equal to a3:"
                           + Arrays.deepEquals(e1, e3)); 
    } 
}

输出：

Check if e1 is equal to e2:true
Check if e2 is equal to e3:false
Check if a1 is equal to a3:false

Equals() vs deepEquals()

虽然Arrays.equals()可在单维数组上正常工作，但它无法检查多维数组的相等性。尽管Arrays.deepEquals()可以在所有数组上使用，无论其尺寸如何。

参考：
https://docs.oracle.com/javase/8/docs/api/java/util/Arrays.html#deepEquals-java.lang.Object:A-java.lang.Object:A-

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