在扫描仪中返回包含char c的字符串 [英] returning string containing char c in scanner

问题描述

尝试创建方法findNewLineWithChar()，该方法返回String并接受扫描程序scn和字符c.它返回包含c的扫描仪行.

Trying to create a method findNewLineWithChar() which returns a String and accepts a Scanner scn and a char c. It returns the line of the scanner which contains c.

我尝试使用字符串来存储currentLine的值，但是它似乎使我的代码复杂，并且始终无法提供任何答案.我很想使用String []，但得到了NullPointerException.我到底在做什么错?

I've tried using a string to store the value of currentLine, but it seemed to convolute my code and not provide any answers anyways. I would love to use a String[], but I get a NullPointerException. What am I exactly doing wrong?

public static String findLineWithChar(Scanner scn, char c) {
     /*
      * findLineWithChar returns line in scanner if line has char c
      * @param scanner
      * @param c
      */

        String result = "";
        String[] stringArray = new String[10]; //accepts max 10 lines

        int counter = 0; //populate string array from scn
        while(scn.hasNextLine()) {
            stringArray[counter] = scn.nextLine();
            counter++;
        }

        //iterate through each element in string array
        for (int i = 0; i < 10; i++) {
            if (stringArray[i].contains(c + "")) {
                result = stringArray[i];
                System.out.println(stringArray[i]);
                break;
            } else {
                result = "";
            }
        }

        return result;
    }

如果我提供真实的陈述，它会起作用， findLineWithChar(new Scanner("Look here!\nLook there!\nExtra extra!"), 'x')返回Extra extra!，但是findLineWithChar(new Scanner("Look here！\ nLook there！\ nExtra extra！")，'q')返回NullPointerException.我该如何处理?

It works if I feed it a true statement, findLineWithChar(new Scanner("Look here!\nLook there!\nExtra extra!"), 'x') returns Extra extra!, but findLineWithChar(new Scanner("Look here!\nLook there!\nExtra extra!"), 'q') returns a NullPointerException. How do I deal with this?

推荐答案

首先，Javadoc注释在方法之前(并以/**开头).其次，这里不需要数组；只是保持计数以确保您消耗的行数不超过十行(假设这是必要的).当找到匹配的行时，我将返回而不是设置返回变量并中断循环.我也希望 String.indexOf(int) 构建一个字符String进行比较.并且，为没有匹配项时添加默认的返回值.喜欢，

First, Javadoc comments go before the method (and start with /**). Second, you don't need an array here; just keep a count to make sure you don't consume more than ten lines (assuming that's necessary). Instead of setting a return variable and breaking the loop, I would return when a matching line is found. I would also prefer String.indexOf(int) to building one character String(s) for comparison. And, add a default return value for when nothing matches. Like,

/**
 * findLineWithChar returns line in scanner if line has char c
 * 
 * @param scanner
 * 
 * @param c
 */
public static String findLineWithChar(Scanner scn, char c) {
    int counter = 0;
    while (scn.hasNextLine() && counter < 10) {
        String line = scn.nextLine();
        if (line.indexOf(c) > -1) {
            return line;
        }
        counter++;
    }
    return "";
}

这篇关于在扫描仪中返回包含char c的字符串的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！