Question

我的挑战是使用用户输入查找字符串中元素的总值。用户输入应如下：1,2,3,4,5,6,7 ......

当我尝试使用StringTokenizer时遇到问题所以我使用了split（）方法，但是根据我是否使用（i + i）或（ + = i）在第二个for循环中。

// Libraries
import java.util.Scanner;
import java.util.StringTokenizer;

public class Project_09_8
{

    public static void main(String[] args) 
    {

    // Create instance of Scanner class
    Scanner kb = new Scanner(System.in);

    // Variables
    String input;                       // Holds user input
    String [] result;                   // Holds input tokens in an array
    int i = 0;                          // Counter for loop control

    // User input
    System.out.print("Please enter a positive whole number, separated by commas: ");
    input = kb.nextLine();
    result = input.split(",");

    // Converts input String Array to Int Array
    int [] numbers = new int [result.length];                

    // Loop through input to obtain each substring
    for (String str: result) {
        numbers[i] = Integer.parseInt(str);
        i++;
    }

    // Receive this output when printing to console after above for loop [I@10ad1355. 

    /*
    // Loop to determine total of int array
    int sum = 0;                        // Loop control variable
    for (int j : numbers) {
         sum += i;
         //sum = i + i;                
     }

    // Print output to screen
    System.out.println("\nThe total for the numbers you entered is: " + sum);
    */

    } // End main method

} // End class

Answer 1

在Java 8中，您可以让自己摆脱痛苦

代码：

String s = "1,2,3,4,5,6,7";
String[] sp = s.split(",");
//Stream class accept array like Stream.of(array)
// convert all String elements to integer type by using map
// add all elements to derive summation by using reduce 
int sum = Stream.of(sp)
                .map( i -> Integer.parseInt(i))
                .reduce(0, (a,b) -> a+b);
System.out.println(sum);

输出：

Answer 2

由于您已经在使用Scanner，因此可以使用useDelimiter方法为您分割逗号。

扫描程序还有一个nextInt()来解析/从String转换为int

    Scanner s = new Scanner(System.in)
                    .useDelimiter("\\s*,\\s*");
    int sum = 0;
    while(s.hasNextInt()){
         sum += s.nextInt();
    }
    System.out.println(sum);

Answer 3

我建议您使用\\s*,\\s*拆分（可选）空格，在需要时声明变量并在一个循环中添加总和（不转换为int[]副本），例如，

public static void main(String[] args) {
    // Create instance of Scanner class
    Scanner kb = new Scanner(System.in);
    System.out.print("Please enter a positive whole number, "
        + "separated by commas: ");
    String input = kb.nextLine();
    String[] result = input.split("\\s*,\\s*");
    int sum = 0;
    for (String str : result) {
        sum += Integer.parseInt(str);
    }
    System.out.println(Arrays.toString(result));
    System.out.printf("The sum is %d.%n", sum);
}

查找String中元素的总值

3 个答案: