Java>>运算符查找字符是否唯一 [英] Java >> operator find if characters are unique

问题描述

我不太清楚这段代码是如何工作的：

I am not really sure how this code works:

public static boolean isUniqueChar2(String str) {
    int checker = 0;

    for (int i = 0; i < str.length(); ++i) {
        int val = str.charAt(i) - 'a';
        System.out.println(str.charAt(i) );
        System.out.println(val);
        if ((checker & (1 << val)) > 0)
            return false;
        checker |= (1 << val);
    }
    return true;
}

特别是我不明白>> operator和checker的作用

In particular I do not understand particular >> operator and the role of checker

推荐答案

看起来这种方法只适用于小写字母。 checker 变量是一个初始化为所有 0 的32位位图。代码 1<< val 取1并将其移动到 val 的位置，其代表字母表的字母（a = 0，b = 1，c = 2等）。 if（（checker&（1<< val））> 0）返回 false 除0以外，表示已重复了一封信。循环中的最后一行 checker | =（1 <; val）; 设置位置 val 在下一次迭代之前。

It looks like this method is only designed to work for lower-case letters. The checker variable is a 32-bit bitmap initialized to all 0s. The code 1 << val takes a 1 and shifts it into the position of val, which represents a letter of the alphabet (a=0, b=1, c=2, etc.). if ((checker & (1 << val)) > 0) returns false because any value other than 0 would indicate that a letter had been repeated. The last line in the loop, checker |= (1 << val); sets the bit at position val before the next iteration.

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