Java重回困境

Question

Okay so I have the following code and no matter what it returns to me a -1. I want to have it so that if the id matches then it returns and index but if it doesn't match after running through the whole data set it returns a negative one. Where am I going wrong here:

public class StudentCollection {

private String[] ids = new String[] {"Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty"}; // keeps identification numbers of students 
private String [] names = new String[] {"Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty","Empty"};;  // keeps the names of students 
private int size = 0; // number of students currently in the collection 


private int findIndex(String id) {
    int noIndex = 1;
    for (int i=0;i<ids.length;i++){
        if((ids[i].equalsIgnoreCase(id))){
            System.out.println("The index of this student is " +i);
            }

        else  {
            noIndex = -1;
            System.out.println(noIndex);
            break;}     
    }

    return noIndex;
}

Answer 1

Here is the solution where if index is found then its number is returned, else if it isn't after checking whole array, -1 is returned and appropriate Strings are printed.

private int findIndex(String id) {
    int noIndex = -1;
    for (int i = 0; i < ids.length; i++) {
       if (ids[i].equalsIgnoreCase(id)) {
          System.out.println("The index of this student is " + i);
          return i;
       }
    }
    System.out.println(noIndex);
    return noIndex;
}

You can also use Java 8 Stream:

private int findIndex(String id) {
    OptionalInt index = IntStream.rangeClosed(0, ids.length-1)
                                 .filter(i -> ids[i].equalsIgnoreCase(id))
                                 .findFirst();
    if(index.isPresent()) {
        int i = index.getAsInt();
        System.out.println("The index of this student is " + i);
        return i;
    }
    System.out.println(-1);
    return -1;
}

Answer 2

Right now you have it so when ids[i].equalsIgnoreCase(id) is true, it will set noIndex to -1 (in the else statement) and break the for loop which will make it return -1. When that is false, it will print out the index. Like everyone else has already posted, here is the code to find the index.

private int findIndex(String id) {
    for (int i=0;i<ids.length;i++){
        if(ids[i].equalsIgnoreCase(id)){
            return i;
        } 
    }

    return -1;
}

Answer 3

i think you need something like this :

private int findIndex(String id) {

    for (int i=0; i<ids.length; i++){

        if(ids[i].equalsIgnoreCase(id)){

            System.out.println("The index of this student is " +i);

            return i;   
        }
    }

    return -1;
}