java_关于scanner对象的nextInt()方法和nextLine()方法再oj中可能出现的报错问题

文章目录

• 是否会报错：处理代码的健壮性，另一方面就是收输入文件中，文件末尾是否有回车符的影响
• example

是否会报错：处理代码的健壮性，另一方面就是收输入文件中，文件末尾是否有回车符的影响

example

 
/*
* Input:
有多组数据测试，以输入 0 结束。
 
第一行输入一个数字 t ，表示接下来有 t 行输入，分别代表 t 只飞龙的飞行方程。
* 每一行的输入格式如下：“3X 2 6 Y 5 3 Z 2”表示飞行方程：“3*x^2+ 6*y^5 + 3 * z ^2”，
* 同样，会存在如下的输入：“1X 3 2 X 3 6 Y 2 3 Z 0”表示飞行方程：“3* x ^ 3 + 6 * y ^ 2 + 3 * z ^ 0”。
* 并保证每行相对应的输出为“a* x ^ (n1) + b * y ^ (n2) + c * z ^ (n3)”，
* 输入的各项系数和次数都为0~ 9的数字，以及输入只会有“X”、“Y”和“Z”三个字母。
* 输入一行不会超过2000个字符长度。
* 输入数据均在int范围内。（若出现幂次为0，则视为1。）
 
Output:
对于每组测试，输出“Case#k: ”，首先，k从1开始标号。
 
对于每个飞行方程，输出“a* x ^ (n1) + b * y ^ (n2) + c * z ^(n3)”
* 表示求导后的结果。详细参见样例，每行中会存在空格，注意空格的输出控制。
 
 
Sample Input:
*/
/*
 
2
1 X 3 2 X 3 6 Y 2 3 Z 0
3 X 2 6 Y 5 3 Z 2
4
9 X 9 9 X 9 9 X 9 9 X 9 9 X 9
9 X 9 9 Y 9
9 X 9 9 Z 9
9 Y 9 9 Z 9
0
 
*/
/*
Sample Output:
Case #1:
9 * X ^ 2 + 12 * Y ^ 1 + 3
6 * X ^ 1 + 30 * Y ^ 4 + 6 * Z ^ 1
Case #2:
405 * X ^ 8
81 * X ^ 8 + 81 * Y ^ 8
81 * X ^ 8 + 81 * Z ^ 8
81 * Y ^ 8 + 81 * Z ^ 8
*
* */
package acmInJava.test_scanner;
 
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
 
public class Main {
 
    public static void main(String[] args) throws FileNotFoundException {
        /*simulate the input like the oj :the end of the input file without the enter/return key;*/
        File file = new File("/D:\\OneDrive - pop.zjgsu.edu.cn\\javaProject\\src\\acmInJava\\test_scanner/dataIn.txt");
        Scanner sc = new Scanner(file);
        int count = 0;
        while (true) {
            int t = sc.nextInt();
            /* the error maybe triggered in here :*/
            sc.nextLine();
                /*if we put the sc.nextLine() out of the if judge,then the the code will throw error
                * due to the:java.util.NoSuchElementException: No line found
                * well,this depend on the data in the input file:if the file is end with an enter key,the code is still worked;if without enter key ,it will throw runtime error */
 
            /*correct pattern 1:
            * if(sc.hasNextLine()){
                sc.nextLine();
            * }
            * */
            
 
            // System.out.println("numOfEquality="+t);
            // System.out.println("test the content:"+sc.nextLine()+"!!!");
            /**
             * int java.util.Scanner.nextInt() Scans the next token of the input as an int.
             *
             * An invocation of this method of the form nextInt() behaves in exactly the
             * same way as the invocation nextInt(radix), where radix is the default radix
             * of this scanner.
             *
             * Returns: the int scanned from the input Throws: InputMismatchException - if
             * the next token does not match the Integer regular expression, or is out of
             * range NoSuchElementException - if input is exhausted IllegalStateException -
             * if this scanner is closed
             */
            if (t == 0) {
                break;
            }
 
            /**
             * String java.util.Scanner.nextLine() Advances(go forward) this scanner past
             * the current line and returns the input that was skipped. This method returns
             * the rest of the current line, excluding any line separator at the end. The
             * position is set to the beginning of the next line.
             *
             * Since this method continues to search through the input looking for a line
             * separator, it may buffer all of the input searching for the line to skip if
             * no line separators are present.
             *
             * Returns: the line that was skipped Throws: NoSuchElementException - if no
             * line was found IllegalStateException - if this scanner is closed
             */
            // sc.nextLine();// place the sc.nextLine() after the if-break ,the code is accepted
            // System.out.println("test the content:"+sc.nextLine()+"!!!");
 
            System.out.println("Case #" + (++count) + ":");
            for (int i = 0; i < t; ++i) {
 
                int x_1 = 0, x_exp = 0;
                int y_1 = 0, y_exp = 0;
                int z_1 = 0, z_exp = 0;
                String line = "";
                if (sc.hasNextLine()) {
 
                    line = sc.nextLine();
                }
                String[] strs = line.split(" ");
                for (int j = 0; j < strs.length; ++j) {
                    if ("X".equals(strs[j])) {
                        x_1 += Integer.parseInt(strs[j - 1]);
                        x_exp = Integer.parseInt((strs[j + 1]));
                        if (x_exp == 0)
                            x_exp = 1;
                    } else if ("Y".equals(strs[j])) {
                        y_1 += Integer.parseInt(strs[j - 1]);
                        y_exp = Integer.parseInt((strs[j + 1]));
                        if (y_exp == 0)
                            y_exp = 1;
                    } else if ("Z".equals(strs[j])) {
                        z_1 += Integer.parseInt(strs[j - 1]);
                        z_exp = Integer.parseInt((strs[j + 1]));
                        if (z_exp == 0)
                            z_exp = 1;
                    }
 
                }
 
                x_1 *= x_exp;
                --x_exp;
                y_1 *= y_exp;
                --y_exp;
                z_1 *= z_exp;
                --z_exp;
 
                if (x_1 != 0) {
                    if (x_exp != 0)
                        System.out.print(x_1 + " * X ^ " + x_exp);
                    else
                        System.out.print(x_1);
 
                    if (y_1 != 0 || z_1 != 0)
                        System.out.print(" + ");
                }
 
                if (y_1 != 0) {
                    if (y_exp != 0)
                        System.out.print(y_1 + " * Y ^ " + y_exp);
                    else
                        System.out.print(y_1);
 
                    if (z_1 != 0)
                        System.out.print(" + ");
                }
 
                if (z_1 != 0) {
                    if (z_exp != 0)
                        System.out.print(z_1 + " * Z ^ " + z_exp);
                    else
                        System.out.print(z_1);
                }
 
                System.out.println();
            }
        }
    }
}