java - 返回 Hash Map 对象多个值

Question

嘿，这里有很棒的人!关注这个问题太久了，找不到答案。我需要显示状态(键)和资本对象； name、pop 和 square Mi(值: string、int 、int)。我怎样才能显示这些？当我正常运行(键，值)时运行 null 我尝试 .get 并出现静态错误。请帮忙!？

// Other class get set

public class Capital  {

    public String name;
    public int pop;
    public int sqM;

    public Capital(String nameIn, int popIn, int sqMIn){
        this.name = nameIn;
        this.pop = popIn;
        this.sqM = sqMIn;
    }
    public String getName(){
        return name;
    }
    public void setName(String name){
        this.name = name;
    }
    public int getPop(){
        return pop;
    }
    public void setPop(int pop){
        this.pop = pop;
    }
    public int getSquare(){
        return sqM;
    }
    public void setSquare(int sqM){
        this.sqM = sqM;
    }
}

public class App {
    
    public static void main(String[] args){
        
        HashMap<String, Capital> StateCap = new HashMap<>();
        
        Capital capitalOne = new Capital("Montgomery", 258, 768);
        StateCap.put("Alabama", (capitalOne));
        Capital capitalTwo = new Capital("Juneau", 576, 94);
        StateCap.put("Alaska", (capitalTwo));
        
        Set<String> keys = StateCap.keySet();
        
         for (String state : keys) {
            //This is where I need help I believe.

Answer 1

好吧，你已经很接近了。您只需多了解一点 HashMap 的功能即可。给你:

    for (String state : keys) {
       // Get the value i.e. `Capital` object corresponding to the `key` i.e. `State`
        Capital cap = StateCap.get(state);
        System.out.println(cap.getName());
        System.out.println(cap.getPop());
        .
        .
        blah blah
    }

另请阅读 entrySet() 方法。

注意::遵循变量的命名约定(例如:StateCap 到 stateCap)。