比較ArrayList到字符串

Question

//我的問題是，在方法cancelOrder中字符串[] waitingList []至少沒有被看到，這是我的想法。

public static String[] canceledOrder(String[] waitingList,String[] waitingList1,String []waitingList2,String[] waitingList3){//I've decided to pass these string [] hoping the string from the other methods will now be seen in canceledOrder(); 
      Scanner in = new Scanner (System.in); 
      int option; 
      System.out.println("Select the event you want to cancel :\n"); 
      events(); 
      option= in.nextInt(); 
      in.nextLine(); 
      System.out.println("Person on wait list is " + waitingList[name]); 
      switch (option){ 

      case 1: 
       System.out.println("Please enter your name:\n"); 
       canceledname = in.nextLine(); 
       System.out.println("name:" + canceledname); 



       for (String s : myStringList) { 
        if(s.equals(canceledname)){ 

         s = waitingList[name]; 

         System.out.println("The new name is\n" + s); 

         name++; 
        } 
        return s; // I want it to now return waitingList[name] 
       } 

       break; 

Answer 1

我可能是錯的，但是你要遍歷數組列表，看看列表中的任何值等於cancelledName？

如果是的話，你可能會想是這樣的

for (String s : myStringList) { 
    if(s.equals(canceledname)){ 

     k = waitingList[name]; 

     System.out.println("The new name is" + k); 

    name++; 
    } 
} 

編輯：可能出現的問題的解決方案

// declare array of Attendees, capacity is 20 
// I would rather use ArrayList, but it seems you're trying to use array 
String attendees[] = new String[20]; 

// delcare wait list 
String waitList[] = new String[2]; 

// declare int for tickets sold 
int ticketsSold = 0; 
// declare waitlist 
int waitlistCount = 0; 

// prompt buyers for purchase of tickets 
// ticketsSold = ticketsSold + 1 or 2 depending on tickets 
// if ticketsSold is 20 do not sell tickets and send to waiting list 
// Do this until full 

// if ticketsSold = 20 
// prompt user to go on wait list 
// if yes, ask how many tickets 
// if tickets requested for waitlist exceeds current waitlist + tickets requested 
     // System.out.println("Sorry, waitlist is full"); 
// else prompt for user name 
String name = in.nextLine(); 
waitlist[waitListCount] = name; 

// here's the part I think you're having problems with 
// if person is deleted from attendees 
// get name of person not attending 
int i = 0; 
while (!cancelledName != attendees[i]) { 
    i++ 
} 

// replace attendees index with waitlist Name 
attendees[i] = waitlist[0]; 

// move the waitlist forward 
waitlist[0] = waitlist[1]; 
waitlist[1] = null; 

這是我能想到的，只要邏輯是最好的。如果你的邏輯是聲音，看起來和我的相似，只關注底部，我認爲你遇到的問題最多

Answer 2

你要做的就是......你試圖找出如果ArrayList等於String。這從來都不是真的，因爲它們不是同一類型的。

我想你想要的是找出ArrayList的字符串表示是否等於字符串canceledname。

myStringList.toString().equals(canceledname) 

Answer 3

我想你想找出是否存在myStringListcanceledname，對於你必須穿越myStringList - 沒有辦法繞過它。

for(String name : myStringList){ 
    if(name.equals(canceledname){ 
      // continue... 
      k = waitingList[name]; 
      System.out.println("The new name is" + k); 
      i++; 
      name++; 
    } 
} 

對於那種比較會更好的名字在Set保存例如：

HashSet<String> names = new HashSet<String>(); 
// here you'll add the names to the hash-set 
// using: names.add("whatever"); 
// ... 

//and now: 
if(names.get(canceledname) != null){ 
     // continue ... 
} 

Answer 4

你不能比較ArrayList和String，而是使用contains方法來查找元素是否存在於數組列表。

boolean isElementExists = myStringList.contains(canceledname); 

if(isElementExists) { 
    // other codes here 
} 

見API：ArrayList#contains()