線性搜索期間二維數組中的數組索引超出範圍錯誤

Question

我正在編寫一個程序，該程序應該像檢票機一樣工作。它會顯示可能的座位選擇圖表及其價格，並詢問用戶是否希望按座位數量或價格選擇座位。它的工作原理就像假設在座位上按數字排序，但是當我嘗試按價格查找座位時，我得到的數組索引超出了界限錯誤。我很困惑，因爲它假設在零點開始線性搜索。我不明白爲什麼會出現這個錯誤。

import java.util.Scanner; 

public class FindTicket{ 
    public static void main(String[] args){ 
    String answer="number"; 
    Scanner kb=new Scanner(System.in); 
    int[][] seats= { 
     {10,10,10,10,10,10,10,10,10,10}, 
     {10,10,10,10,10,10,10,10,10,10}, 
     {10,10,10,10,10,10,10,10,10,10}, 
     {10,10,20,20,20,20,20,20,10,10}, 
     {10,10,20,20,20,20,20,20,10,10}, 
     {10,10,20,20,20,20,20,20,10,10}, 
     {20,20,30,40,40,40,30,30,20,20}, 
     {20,30,30,40,50,50,40,30,30,20}, 
     {30,40,50,50,50,50,50,50,40,30} 
    }; 

    printChart(seats); 
    do{ 
     System.out.println("Would you like to choose a seat by number, price, or quit?"); 
     answer = kb.nextLine(); 
     if(answer.equals("price")){ 
     sellSeatbyPrice(seats);} 
     if(answer.equals("number")){ 
     sellSeatbyNumber(seats);} 
     printChart(seats); 
    }while(!answer.equals("quit")); 
    } 

    public static void printChart(int[][] seats){ 
    for (int i=0; i<seats.length; i++) 
    { 
     for(int j=0; j<seats[0].length; j++) 
     { 
     System.out.printf("%8d", seats[i][j]); 
     } 
     System.out.println(); 
    } 
    } 

    public static int[][] sellSeatbyPrice(int[][] seats){ 
    Scanner kb=new Scanner(System.in); 
    int ticketprice; 
    int row = 0, col = 0; 
    boolean found = false, seatavaliable=true; 
    do{ 
     System.out.println("What is your prefered ticket price?"); 
     ticketprice=kb.nextInt(); 
     while (row<seats.length && !found){ 
     do{ 
      if(seats[row][col] == ticketprice){ 
      found = true;} 
      else{ 
      col++; } 
     }while(col<seats[0].length &&!found); 
     if(seats[row][col] == ticketprice){ 
      found = true;} 
     else{ 
      row++;} 
     } 
     if(found){ 
     seats[row][col] = 0; } 
     else { 
     System.out.println("Seat not found at specified price."); 
     seatavaliable=false;} 
    }while(seatavaliable==false); 

    return seats; 
    } 

    public static int[][] sellSeatbyNumber(int[][] seats){ 
    Scanner kb=new Scanner(System.in); 
    int row = 0, col = 0; 
    int editedrow, editedcol; 
    boolean seatavaliable = true; 
    do{ 
     System.out.println("What is your prefered seat number? Please enter row then column."); 
     row=kb.nextInt(); 
     col=kb.nextInt(); 
     editedrow = 9-row; 
     editedcol = col - 1; 
     if(seats[editedrow][editedcol] > 0){ 
     seats[editedrow][editedcol] = 0;} 
     else{ 
     System.out.println("Seat is not avaliable."); 
     seatavaliable=false;} 
    }while(seatavaliable==false); 

    return seats; 
    } 

} 

Answer 1

這是因爲do...while。

當這段代碼完成後，col將會大於數組的長度。

看的意見：

public static int[][] sellSeatbyPrice(int[][] seats){ 
    Scanner kb=new Scanner(System.in); 
    int ticketprice; 
    int row = 0, col = 0; 
    boolean found = false, seatavaliable=true; 
    do{ 
     System.out.println("What is your prefered ticket price?"); 
     ticketprice=kb.nextInt(); 
     while (row<seats.length && !found){ 
     do{ 
      if(seats[row][col] == ticketprice){ 
      found = true;} 
      else{ 
      col++; } // this line, in the last iteration, will make col=seats[0].length 
     }while(col<seats[0].length &&!found); 
     if(seats[row][col] == ticketprice){ //col with value greater than it should. 
      found = true;} 
     else{ 
      row++;} 
     } 
     if(found){ 
     seats[row][col] = 0; } 
     else { 
     System.out.println("Seat not found at specified price."); 
     seatavaliable=false;} 
    }while(seatavaliable==false); 

    return seats; 
    } 

Answer 2

的nextInt()方法離開\n（端線）符號，並且由nextLine()立即回升，跳過下一個輸入。你想要做的是使用nextLine()的一切，後來又對其進行分析：

String nextIntString = keyboard.nextLine(); //get the number as a single line 
int nextInt = Integer.parseInt(nextIntString); //convert the string to an int 

這是迄今爲止最簡單的方法，以避免出現問題 - 不要混合你的「下一個」的方法。之後只使用nextLine()，然後解析int或單獨的單詞。

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不能關閉另一個Scanner因爲它然後關閉底層InputStream，因此第一Scanner不再能夠從同一InputStream讀，你會得到一個NoSuchElementException。

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最後要注意的：你應該總是關閉Scanner，當你用它做，以節省系統資源。