在Java中等于与Arrays相等
在Java中等于与Arrays相等
array1.equals(array2);Arrays.equals(array1, array2);
海绵宝宝撒浏览 591回答 3
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不负相思意
array1.equals(array2)是相同的array1 == array2，即它是否是同一个数组。正如@Alf所指出的，这并不是大多数人所期望的。Arrays.equals(array1, array2)比较数组的内容。类似array.toString()可能不是很有用，您需要使用Arrays.toString(array). -
心有法竹
这是一个臭名昭著的问题：.equals()因为数组坏了，请永远不要使用它。也就是说，它并没有像“某人以一种非常错误的方式去做”那样“被打破”-它只是在做定义上的事情，而不是通常预期的事情。所以对于纯粹主义者来说，这是非常好的，这也意味着，永远不要用它。现在预期的行为equals就是比较数据。默认行为是比较身份，如Object没有任何数据(对于纯粹主义者：是的，但这不是重点)；假设是，如果你需要的话equals在子类中，您将实现它。在数组中，您没有实现，因此不应该使用它。所以区别在于，Arrays.equals(array1, array2)作品如你所料(即比较内容)，array1.equals(array2)回到Object.equals实现，这反过来比较身份，因此更好地由==(对纯粹主义者来说：是的我知道null).问题是，甚至Arrays.equals(array1, array2)如果数组的元素没有实现，就会咬死你。equals恰到好处。我知道，这是一个非常幼稚的说法，但有一个非常重要的不太明显的例子：考虑一个2D数组。Java中的2D数组是数组的数组，而数组是equals是坏的(或者如果你愿意的话是没用的)，所以Arrays.equals(array1, array2)不会像你期望的那样在二维数组上工作。希望能帮上忙。 -
Qyouu
深入了解这两种方法的实现情况：array1.equals(array2);/** * Indicates whether some other object is "equal to" this one. * <p> * The {@code equals} method implements an equivalence relation * on non-null object references: * <ul> * <li>It is <i>reflexive</i>: for any non-null reference value * {@code x}, {@code x.equals(x)} should return * {@code true}. * <li>It is <i>symmetric</i>: for any non-null reference values * {@code x} and {@code y}, {@code x.equals(y)} * should return {@code true} if and only if * {@code y.equals(x)} returns {@code true}. * <li>It is <i>transitive</i>: for any non-null reference values * {@code x}, {@code y}, and {@code z}, if * {@code x.equals(y)} returns {@code true} and * {@code y.equals(z)} returns {@code true}, then * {@code x.equals(z)} should return {@code true}. * <li>It is <i>consistent</i>: for any non-null reference values * {@code x} and {@code y}, multiple invocations of * {@code x.equals(y)} consistently return {@code true} * or consistently return {@code false}, provided no * information used in {@code equals} comparisons on the * objects is modified. * <li>For any non-null reference value {@code x}, * {@code x.equals(null)} should return {@code false}. * </ul> * <p> * The {@code equals} method for class {@code Object} implements * the most discriminating possible equivalence relation on objects; * that is, for any non-null reference values {@code x} and * {@code y}, this method returns {@code true} if and only * if {@code x} and {@code y} refer to the same object * ({@code x == y} has the value {@code true}). * <p> * Note that it is generally necessary to override the {@code hashCode} * method whenever this method is overridden, so as to maintain the * general contract for the {@code hashCode} method, which states * that equal objects must have equal hash codes. * * @param obj the reference object with which to compare. * @return {@code true} if this object is the same as the obj * argument; {@code false} otherwise. * @see #hashCode() * @see java.util.HashMap */public boolean equals(Object obj) { return (this == obj);}同时：Arrays.equals(array1, array2);/** * Returns <tt>true</tt> if the two specified arrays of Objects are * <i>equal</i> to one another. The two arrays are considered equal if * both arrays contain the same number of elements, and all corresponding * pairs of elements in the two arrays are equal. Two objects <tt>e1</tt> * and <tt>e2</tt> are considered <i>equal</i> if <tt>(e1==null ? e2==null * : e1.equals(e2))</tt>. In other words, the two arrays are equal if * they contain the same elements in the same order. Also, two array * references are considered equal if both are <tt>null</tt>.<p> * * @param a one array to be tested for equality * @param a2 the other array to be tested for equality * @return <tt>true</tt> if the two arrays are equal */public static boolean equals(Object[] a, Object[] a2) { if (a==a2) return true; if (a==null || a2==null) return false; int length = a.length; if (a2.length != length) return false; for (int i=0; i<length; i++) { Object o1 = a[i]; Object o2 = a2[i]; if (!(o1==null ? o2==null : o1.equals(o2))) return false; } return true;}
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