如何使用 java 语句从字符串数组的字符串数组中获取索引以打印语句？

Question

public static void main (String[] args) throws java.lang.Exception{
    ArrayList friends = new ArrayList<>(asList("Danny", "Benni", "Marcus", "Pat"));
    ArrayList Places = new ArrayList<>(asList("Paris", "Brasil", "Miami", "Jamaica"));
    ArrayList Gifts = new ArrayList<>(asList("Snacks", "Photos", "Instrument", "Whine"));
    
    ArrayList[] travelgoals = new ArrayList<>{Places, Gifts};
    
    for (int b = 0; b > friends.length; b++){
        if(b > Places.length) {
            System.out.println(Places.get().Random((0), Places.length);
        }if (b > Gifts.length) {
            System.out.println(Gifts.get().Random((0), Gifts.length);
        }
    }else {
        System.out.println("Looks like you got off scottfree!");
    }
}

您好，我正在尝试使用字符串数组来打印位置中的随机目标，但我认为我还远远不够。

Answer 1

您要查找的属性是“大小”。

ArrayList和数组在这方面是不同的。你用“arr.length”得到一个数组的长度，用“arrList.size()”得到一个ArrayList的长度（或大小）。

还可以使用 Random 类的 nextInt 方法生成大小范围内的随机索引。

下面是类似于您尝试执行的代码，它为每个朋友挑选随机礼物和地点。

public static void main (String[] args) throws java.lang.Exception{
    ArrayList<String> friends = new ArrayList<>(Arrays.asList(new String[]{"Danny", "Benni", "Marcus", "Pat"}));
    ArrayList<String> places = new ArrayList<>(Arrays.asList(new String[]{"Paris", "Brasil", "Miami", "Jamaica"}));
    ArrayList<String> gifts = new ArrayList<>(Arrays.asList(new String[]{"Snacks", "Photos", "Instrument", "Whine"}));
        
    Random rand = new Random();//This is the Random class that can be used to generate random number. In this case Integers
    

    //just a for loop iterating through all friends
    //This will pick a random element from each of places and gifts
    //You can get an element of a list by using the get 
    //method(arrList.get(index))

    for(String friend : friends){
        System.out.println(places.get(rand.nextInt(places.size())));
        System.out.println(gifts.get(rand.nextInt(gifts.size())));
     }
}

编辑：使用 Map 添加了一种更具可扩展性的方式，因为如果您继续增加属性，维护起来会很忙。

Map<String, ArrayList<String>> mapOfProperties = new HashMap<>();

mapOfProperties.put("friends",Arrays.asList(new String[]{"Danny", "Benni", "Marcus", "Pat"}));

mapOfProperties.put("places",Arrays.asList(Arrays.asList(new String[]{"Paris", "Brasil", "Miami", "Jamaica"}));

mapOfProperties.put("gifts",Arrays.asList(new String[]{"Snacks", "Photos", "Instrument", "Whine"}));

Set<String> keysOfMap = mapOfProperties.keySet(); 

Random rand = new Random();

for(int i=0;i<map.get("friends").size();i++){
    for(String keyName : keysOfMap){
       int keyIndex = rand.nextInt(mapOfProperties.get(keyName).size());
       //can put mapOfProperties.get(keyName) in a temp arrayList as well
       System.out.print(mapOfProperties.get(keyName).get(keyIndex));
    }
}