接受字符串输入到数组中并检查数组中字符串的可用性

Question

So I am completely new to java, and I want to create a code to accept string inputs from a user, and store it into an array. After this in the next statement, I will type a value into the terminal, and I want the code to compare my string input to one of the strings in the array and print available on the terminal when the string is available and vice versa. The first part of my code was right (hopefully) but I had a problem in comparing the strings. I feel it doesn't check the strings with my input in the code. Here is my code, Could anyone please help me with this? Thank you so much.

import java.util.Scanner;
class Course {
 public static void main(String[] args) {
  Scanner sc = new Scanner(System.in);
  String a[] = new String[20] //assuming max 20 strings
  System.out.println("Enter no. of courses");
  int no_of_courses = sc.nextInt(); // number of strings
  if (no_of_courses <= 0)
   System.out.println("Invalid Range");
  else {
   System.out.println("Enter course names:");
   for (int i = 0; i < no_of_courses; i++) {
    a[i] = sc.next(); //accepting string inputs
   }
   System.out.println("Enter the course to be searched:");
   String search = sc.next() //entering a string to search
   for (int i = 0; i < no_of_courses; i++) {
    if (a[i].equals(search)) //I feel the problem is here
     System.out.println(search + "course is available");
     break;
     else
      System.out.println(search + "course is not available");
    }
   }
  }
 }

I expect the output to be

<string> course is available

when my string matches a string in the array and

<string> course is not available

when my entered string doesn't match a string in the array

But there is no output:(

Answer 1

I have modified your code and commented on line where it need to be explained. check it carefully.

import java.util.Scanner;

class Course {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.println("Enter no. of courses");
        int no_of_courses = sc.nextInt(); // number of strings
        String a[] = new String[no_of_courses]; // do not assume when you have proper data.
        if (no_of_courses <= 0)
            System.out.println("Invalid Range");
        else {
            System.out.println("Enter course names:");
            for (int i = 0; i < no_of_courses; i++) {
                a[i] = sc.next(); // accepting string inputs
            }
            System.out.println("Enter the course to be searched:");
            String search = sc.next(); // entering a string to search
            boolean flag = false;
            for (int i = 0; i < no_of_courses; i++) {
                if (a[i].equals(search)) // I feel the problem is here
                {
                    flag = true;//do not print here. just decide whether course is available or not
                    break;
                }
            }
            //at the end of for loop check your flag and print accordingly.
            if(flag) {
                System.out.println(search + "course is available");
            }else {
                 System.out.println(search + "course is not available");
            }
        }

    }
}

Answer 2

class Course {
    public static void main(String[] args)
    {
        Scanner sc = new Scanner(System.in);
        String a[] = new String[20] ;                //assuming max 20 strings
                System.out.println("Enter no. of courses");
        int no_of_courses = sc.nextInt();           // number of strings
        if(no_of_courses <= 0)
            System.out.println("Invalid Range");
            else
            {
                System.out.println("Enter course names:");
                for(int i=0 ; i < no_of_courses ; i++)
                {
                    a[i] = sc.next();                            //accepting string inputs
                }
                System.out.println("Enter the course to be searched:");
                String search = sc.next()   ;             //entering a string to search
                boolean found = false;
                        for(int i = 0 ; i < no_of_courses ; i++)
                        {
                            if(a[i].equalsIgnoreCase(search))                   //I feel the problem is here
                            {
                                **found = true;**
                                break;
                            }   

                            }
                        if(found) {
                            System.out.println(search+ "course is available"); 
                        }else {
                            System.out.println(search+ "course is not available");
                        }
                        }
            }
    }

Answer 3

I noticed a few things - Does your program run to the end? When i copy/pasted into my ide i noticed a few missing semi-colons, and like Yhlas said, your last if/else statement syntax is incorrect.

And this doesn't have anything to do with whether or not your program will give you the right answer, but your last loop will print over and over again because it will check each element in a, and each time it loops and finds a mismatch it will print something out

Answer 4

This is really a good effort and you almost got it. So just a couple of things

1. Since you are inputting the number of courses, just use that value to initialise your array (it's just a good practice to get into to try not initialise things before you actually need them).
2. If you are doing String comparisons and case sensitivity does not matter, rather use .equalsIgnoreCase(String)
3. To solve your problem, you just needed a boolean variable to indicate whether or not you had found a match. Initially this would be FALSE (no match found) and you would run through your array until a match is found. Once found this would be flagged TRUE and you'd break out your loop (which you correctly did).
4. Only once out your loop, you'd print out whether you found a match.

Have a look:

public static void main(String[] args) {
  Scanner sc = new Scanner(System.in);
  System.out.println("Enter no. of courses");
  int no_of_courses = sc.nextInt();           // number of strings
  if (no_of_courses <= 0) {
    System.out.println("Invalid Range");
  } else {
    String a[] = new String[no_of_courses];
    System.out.println("Enter course names:");
    for (int i = 0; i < a.length; i++) {
      a[i] = sc.next();                            //accepting string inputs
    }
    System.out.println("Enter the course to be searched:");
    String search = sc.next();                //entering a string to search
    boolean courseFound = Boolean.FALSE;
    for(int i = 0; i < a.length; i++) {
      if (a[i].equalsIgnoreCase(search)) {
        courseFound = Boolean.TRUE;
        break;
      }
    }
    if(courseFound) {
      System.out.println(search + "course is available");
    } else {
      System.out.println(search + " course is not available");
    }
  }
}

Oh, just for interest (and when you start working with some more advanced constructs), you could always just use stream , which was introduced in Java 8. It'll trim down 12 lines to 5...

if(Arrays.stream(a).anyMatch(i -> i.equalsIgnoreCase(search))) {
  System.out.println(search + " course is available");
} else {
  System.out.println(search + " course is not available");
}