数组列表indexOf总是返回-1 \f25 Java

Question

我正在为课程做一个项目，在这个项目中，你必须制作一个名人堂，并能够添加/删除/搜索/编辑不同种类的乐队。现在，我在搜索特定波段的索引时遇到了问题，因为它总是返回-1，而我不确定为什么。

下面是我的代码：

public class HallofFame
{
    public static ArrayList<Band> hallOfFame = new ArrayList<Band>();
    public static Scanner scan = new Scanner(System.in);
    public static void main(String[]args){
        int a = 0;
        while(a == 0){
            System.out.println("What would you like to do?");
            System.out.println("");
            System.out.println("1. Add");
            System.out.println("2. Remove");
            System.out.println("3. Edit");
            System.out.println("4. Clear");
            System.out.println("5. Search");
            System.out.println("6. Quit");
            System.out.println("");
            String choice = scan.nextLine();
            if(choice.equals ("1")){
                add();
            }
            else if(choice.equals ("2")){
                remove();
            }
            else if(choice.equals ("3")){
                edit();
            }
            else if(choice.equals ("4")){
                clear();
            }
            else if(choice.equals ("5")){
                search();
            }
            else if(choice.equals ("6")){
                quit();
                break;
            }
        }
    }

    public static void add(){
        Scanner booblean = new Scanner(System.in);
        System.out.println("What is the name of the band you would like to add?");
        String name = scan.nextLine();
        System.out.println("What kind of genre is this band?");
        String genre = scan.nextLine();
        System.out.println("How many members are in the band?");
        int numMem = scan.nextInt();
        System.out.println("How many songs does this band have?");
        int numSongs = scan.nextInt();
        System.out.println("How many albums does this band have?");
        int numAlbs = scan.nextInt();
        System.out.println("Is this band currently active?");
        String yesno = booblean.nextLine();
        boolean isActive = false;
        if(yesno.equalsIgnoreCase ("yes")){
            isActive = true;
        }
        Band b1 = new Band(name, genre, numMem, numSongs, numAlbs, isActive);
        hallOfFame.add(b1);
        System.out.println("");
        System.out.println("The band " + name + " has been added to the database.");
        System.out.println("");
    }

    public static void remove(){

    }

    public static void edit(){
        System.out.println("What band info do you want to edit?");
        String searchband = scan.nextLine();
    }

    public static void clear(){
        hallOfFame.clear();
    }

    public static void search(){
        System.out.println("What band name are you searching for?");
        String searchband = scan.nextLine();
        int retval = hallOfFame.indexOf(searchband);
        System.out.println("The band " + searchband + " is at index: " + retval);
    }

    public static void quit(){
        System.exit(0);
    }
}

搜索方法是我遇到问题的方法。

Answer 1

问题是hallOfFame包含Band对象，而您在hallOfFame中搜索String。相反，您可以遍历hallOfFame并将乐队名称与输入的字符串进行比较。

Answer 2

或者，您可以覆盖Band的equals方法，这样indexOf就可以实际工作了。

我想它应该是这样的：

@Override

public boolean equals(Object o) {

  return ((Band) o).name==this.name;

}

Answer 3

您应该同时覆盖equals和hashCode，以使其完美工作。

Overriding equals and hashCode in Java