java - 计算字符串中逗号分隔的正数和负数的总出现次数

Question

我正在尝试实现计算字符串中分别包含正整数、负整数、正 float 和负 float 的数字数量的算法。

字符串是这样的:: 字符串mystring =“-7.5,-1.43,3.4,43.5,-9954.88,949.5,1,3,-45”;

我能够实现计算正整数和负整数的代码，例如

当我运行这段代码时，计数结果是 15 而不是 3。任何人都可以帮助我如何实现忽略正 float 和负 float 的逻辑吗？？？

谢谢。

Answer 1

如果你想实现这个算法，你可以尝试这样的事情:

public static int countIntegers(String input) {
    int count = 0;
    boolean sequenceStarted = false;
    boolean isInteger = false;
    boolean tailSpace = false;
    for (int i = 0; i < input.length(); i++) {
        char c = input.charAt(i);
        if (c == ',') {
            //we got a delimiter; checking that the previous sequence is an integer
            if (sequenceStarted && (isInteger || tailSpace)) count++;
            sequenceStarted = false;
            isInteger = false;
            tailSpace = false;
        } else if (!sequenceStarted && c != ' ') {
            //ignoring all leading spaces
            sequenceStarted = true;
            //we got a digit, + or -; it means that number is started
            if (Character.isDigit(c) || (c == '+' || c == '-') 
                                 && Character.isDigit(input.charAt(i + 1)))
                isInteger = true;
        } else if (sequenceStarted && !Character.isDigit(c)) {
            //the character is not a digit, but maybe it is a tail space?
            tailSpace = (isInteger || tailSpace) && c == ' ';
            isInteger = false;
        }
    }
    return count;
}

此代码考虑了前导空格和尾随空格，并且仅计算整数。例如，对于给定字符串 String mystring = ", 4 ,+-7, ,-,-7.5,-1.43,3.4,43.5, -9954.88 , r949, 1, 3, -45, 0.0, 5s, 7-, 2+2"; 它将打印 4。

当然，如果您只想计算字符串中可能仅包含数字、空格、点和逗号的所有整数，那么 Java 8 解决方案就是您所需要的:

String mystring = "-7.5,-1.43,3.4,43.5, -9954.88, 949.5, 1, 3, -45";
long count =
    // splitting your string by ","
    Arrays.stream(mystring.split(","))
        // converting each string to double
        .map(Double::parseDouble)
        // leaving only integers: if d is equal to Math.floor(d) then it must have an int value
        .filter(d -> Math.floor(d) == d && d != 0)
        .count();
System.out.println(count); //prints 3