如何在Java中找到用户接受的字符串数组的索引？

Question

Accept the string from user eg:[Aamir,Hrithik,Salman] Now when i pass Hrithik it should return its index? How?

public static void main(String[] args)
{
    int str,i;
    String check;
    Scanner sc=new Scanner(System.in);
    System.out.println("Enter string array size: ");
    str=sc.nextInt();
    String arr[]= new String[str];
    System.out.println("Enter elements for String array: ");

    for(i=0;i<str;i++)
    {
        arr[i] = sc.next();
    }
    System.out.println(Arrays.toString(arr));

    System.out.println("Enter the name to check index of it:");
    check=sc.next();
    if(arr[i].equals(check))
    {
        System.out.println(i);
    }
}

Answer 1

Checking a single element of the array arr[i].equals(check) doesn't help much. Note that i hasn't been reset from the previous loop execution, you might get an invalid array index ( i >= arr.length ).

You'd better iterate over all the elements of the array to look for a match:

for(i = 0; i < str; ++i) {
    if (arr[i].equals(check)) {
        System.out.println(i);
        break;
    }
}

Answer 2

Transform the array to a list then use indexOf method.

    String[] arr = {"Aamir","Hrithik","Salman"};
    String target = "Hrithik";
    System.out.println(Arrays.asList(arr).indexOf(target));

Answer 3

You need to add a for loop at the end to loop through the entire array. The following code should work. I have also made some other edits that make the code generally better.

Side note: you should format your code a bit better to make it more readable. On most IDEs, you can auto format code using CTRL/CMD+SHIFT+F .

public static void main(String[] args) {

    int str, i;
    String check;

    Scanner sc = new Scanner(System.in);
    System.out.println("Enter string array size: ");
    str = sc.nextInt();

    String arr[] = new String[str];
    System.out.println("Enter elements for String array: ");

    for (i = 0; i < str; i++) {
        arr[i] = sc.next();
        System.out.println(arr[i]);
    }

    System.out.println("Enter the name to check index of it:");
    check = sc.next();

    for (int j = 0; j < str; j++) {
        if (arr[j].equals(check)) {
            System.out.println(j);
            break;
        }
    }
}

Answer 4

There are multiple ways to return the index of a value inside an array. You can:

Use a loop:

for (i = 0; i < str; i++) {
    if (arr[i].equals(check)) {
        System.out.println("Index of value: " + i);
        break; 
    }
}

Use the Arrays utility class:

System.out.println("Index of value: " + Arrays.asList(arr).indexOf(check));

Use the Apache Commons Lang ArrayUtils class:

System.out.println("Index of value: " + ArrayUtils.indexOf(arr, check));