java - java.util.Arrays 中 equals() 的运行时间是多少？

Question

如标题所述，java.util.Arrays 中 equals() 的运行时间是多少？

例如，如果它比较两个 int[] ，它是否循环遍历数组中的每个元素，所以 O(n)？对于 java 中各个类的 equals() 中的所有 equals()，我们可以假设运行时总是 O(n) 吗？

谢谢。

Answer 1

从源码中抓取(源码值100字:P):

/**
 * Returns <tt>true</tt> if the two specified arrays of ints are
 * <i>equal</i> to one another.  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.  In other words, 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(int[] a, int[] 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++)
        if (a[i] != a2[i])
            return false;

    return true;
}