Java 返回问题

Question

好的，我有以下代码，无论它返回给我一个-1。我想要这样，如果 id 匹配，那么它会返回索引，但如果在运行整个数据集后不匹配，它会返回一个负值。我哪里出错了:

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

这里是如果找到索引则返回其编号的解决方案，否则如果在检查整个数组后没有找到，则返回 -1 并打印适当的字符串。

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;
}

您还可以使用 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;
}