如何检查数组是否包含元素？

Question

I'm new to Java.

I have an array that looks like this (Array) . (I've used Array.toString to print this). This is how the array is made: arraymade . And this is read and made from a file in this format:

Nilsson;Lars;u;g;vg;vg
Svensson;Lena;vg;g;g;vg
Jonsson;Jonas;g;g;vg;g

I'm trying to make a method that returns either "u", "vg" or "g" depending on what the objects array contains.

@Override
public String getKursbetyg() {



    if (Arrays.asList(uppgiftsbetyg).contains("u")) {
        kursbetyg = "u";
        return kursbetyg;

    } else if (Arrays.asList(uppgiftsbetyg).contains("if the array contains 2 vg strings")) {
        kursbetyg = "vg";
        return kursbetyg;

    } else {
        kursbetyg = "g";
        return kursbetyg;
    }

}

This is the code I have now but it doesn't seem to work as it only returns "g" even though the array contains "u".

Also as you can see I want the method to only return vg when 2 vg:s are found because you need 2 vg:s to get the grade vg. So how do I check for double elements here ?

Answer 1

First, you should rethink your requirements. The presence of one string (like u ) does not preclude the absence of the others (like two vg s or a g ) nor does the absence of u and two vg s prove the presence of a g . Your posted examples are already inconsistent in this regard.

Besides that, your method lacks a declaration of the variable kursbetyg and I really hope, you are not modifying a field as a side effect of this “get…” method.

You can search for two occurrences straight-forward by searching a sublist excluding the first occurrence:

public String getKursbetyg() {
    List<String> list = Arrays.asList(uppgiftsbetyg);
    if(list.contains("u")) {
        return "u";
    }
    int index=list.indexOf("vg");
    if(index>=0 && list.subList(index+1, list.size()).contains("vg")) {
        return "vg";
    }
    return "g";
}

a solution closer to your original structure, which also might be considered simpler is

public String getKursbetyg() {
    List<String> list = Arrays.asList(uppgiftsbetyg);
    if(list.contains("u")) {
        return "u";
    } else if(Collections.frequency(list, "vg")>=2) {
        return "vg";
    } else {
        return "g";
    }
}

But it might do more work than necessary by unnecessarily counting occurrences of vg beyond 2 .