Java 带字节数组的deepHashCode

由于某些原因，

Arrays.deepHashCode（）

无法使用

字节[]

还有其他等价物吗？

首先，不需要“深”。这是原始的。你不需要太深

只用

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编辑：为了澄清，Deep意味着深入研究数组中包含的对象。假设您正在处理一个基元，您只需要在计算中使用基元值本身。这就是为什么没有一个Deep方法是围绕原语运行的。

使用deepHashCode确实是正确的。如果您希望包含相同字节的两个字节数组具有等效的哈希代码，您只需要对byte[]数组进行一些额外的强制转换

import java.utils.Arrays;

public class A {
  public static void main(String[] args) {
    byte[] a = {10,32,-43,80};
    byte[] b = {13,-40};
    byte[] c = {10,32,-43,80};
    // A and C will have different hash codes
    System.out.println(a.hashCode());
    System.out.println(b.hashCode());
    System.out.println(c.hashCode());
    // A and C will now have equivalent hash codes
    System.out.println(Arrays.deepHashCode(new Object[]{a}));
    System.out.println(Arrays.deepHashCode(new Object[]{b}));
    System.out.println(Arrays.deepHashCode(new Object[]{c}));
  }
}

这导致输出类似于

// Hash Codes
a = 16130931
b = 26315233
c = 32716405
// Deep hash codes
a = 1250961
b = 1355
c = 1250961

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公认的答案是正确的：使用数组。hashCode为具有相同值的字节[]提供相同的结果。 数组。如果您有嵌套（深层）结构，则需要deepHashCode

import java.util.Arrays;

public class A {

    public static void main(String[] args) {
        byte[] a = {10, 32, -43, 80};
        byte[] b = {13, -40};
        byte[] c = {10, 32, -43, 80};

        System.out.println("NOTE: A and C have identical values, B differs");
        System.out.println("Using byte[].hashCode(): A and C have different hash codes");
        System.out.println("a = " + a.hashCode());
        System.out.println("b = " + b.hashCode());
        System.out.println("c = " + c.hashCode());

        System.out.println("Using Arrays.hashCode(): A and C have identical hash codes");
        System.out.println("a = " + Arrays.hashCode(a));
        System.out.println("b = " + Arrays.hashCode(b));
        System.out.println("c = " + Arrays.hashCode(c));

        System.out.println("Using Arrays.deepHashCode(): A and C have identical hash codes");
        System.out.println("a = " + Arrays.deepHashCode(new Object[]{a}));
        System.out.println("b = " + Arrays.deepHashCode(new Object[]{b}));
        System.out.println("c = " + Arrays.deepHashCode(new Object[]{c}));
    }
}

这将导致输出：

NOTE: A and C have identical values, B differs
Using byte[].hashCode(): A and C have different hash codes
a = 141847843
b = 329849131
c = 1119051810
Using Arrays.hashCode(): A and C have identical hash codes
a = 1250930
b = 1324
c = 1250930
Using Arrays.deepHashCode(): A and C have identical hash codes
a = 1250961
b = 1355
c = 1250961

下面是一个when数组的示例。deepHashCode是必需的

import java.util.Arrays;

public class B {
    public static void main(String[] args) {
        Object[] d = {"abc", "def", new String[]{"ghi"}};
        Object[] e = {"abc", "def", new String[]{"ghi"}};

        System.out.println("NOTE: D and E have identical nested values");
        System.out.println("Using Object[].hashCode(): different");
        System.out.println("d = " + d.hashCode());
        System.out.println("f = " + e.hashCode());

        System.out.println("Using Arrays.hashCode(): still different");
        System.out.println("d = " + Arrays.hashCode(d));
        System.out.println("e = " + Arrays.hashCode(e));

        System.out.println("Using Arrays.deepHashCode(): identical");
        System.out.println("d = " + Arrays.deepHashCode(d));
        System.out.println("e = " + Arrays.deepHashCode(e));
    }
}

输出：

NOTE: D and E have identical nested values
Using Object[].hashCode(): different
d = 241990244
f = 1943487137
Using Arrays.hashCode(): still different
d = 1057745997
e = 709187068
Using Arrays.deepHashCode(): identical
d = 95807651
e = 95807651

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我假设您在

java.util.Arrays

中引用了

deepHashCode（）

，注意：对于任何好奇的人，我在一个单独的答案中为嵌套数组添加了一个deepHashCode示例，这是一种非常好的方法，可以在您的答案=）中为基本数组添加可运行代码；但是，Arrays.hashCode比Arrays.deepHashCode更合适。我修改了您的代码，并添加了一个单独的答案，该答案表明它仍然为给定的输入提供相同的哈希代码，以及当两者不同时的示例。