使用ArrayList作爲構造函數的參數

-1

我想寫一個接受ArrayList（包含整數）作爲其參數之一的類的構造函數。稍後再實例化這個類時，我會傳遞一個適當的，預先填充的值列表，所以我不想在構造函數中創建一個空列表。使用ArrayList作爲構造函數的參數

不幸的是，當我嘗試編譯下面的代碼時，Java吐出了五個錯誤，都與第23行（我的構造函數的定義）有關。任何意見將不勝感激：

/* 
* SumGenerator 
* 
* @author James Scholes 
*/ 

import java.util.ArrayList; 
import java.util.Random; 

public class SumGenerator 
{ 
    // Some initial variables 
    public int timesTable; 
    public int multiple; 

    /* 
    * Constructor 
    * 
    * @param timesTable(int): The times table to use for sum generation 
    * @param limit(int): The highest multiple to use in sum generation 
    * @param previousMultiples(ArrayList<Integer>): The previously used multiples to avoid sum duplication 
    */ 
    public SumGenerator(int timesTable, int limit = 10, ArrayList<Integer> previousMultiples) 
    { 
     this.timesTable = timesTable; 
     Random randomGenerator = new Random(); 

     // Create a list to store our multiples 
     ArrayList<Integer> multiples = new ArrayList<Integer>(); 
     // and add our multiples to it, only if 
     // they haven't been used before 
     for(int i = timesTable; i <= limit; i++) 
     { 
      if(previousMultiples.contains(i)) 
      { 
       continue; 
      } 
      else 
      { 
       multiples.add(i); 
      } 
     } 

     this.multiple = multiples.get(randomGenerator.nextInt(multiples.size())); 
    } 

} 

SumGenerator.java:23: error: ')' expected 
    public SumGenerator(int timesTable, int limit = 10, ArrayList<Integer> previousMultiples) 
               ^
SumGenerator.java:23: error: illegal start of type 
    public SumGenerator(int timesTable, int limit = 10, ArrayList<Integer> previousMultiples) 
                ^
SumGenerator.java:23: error: <identifier> expected 
    public SumGenerator(int timesTable, int limit = 10, ArrayList<Integer> previousMultiples) 
                ^
SumGenerator.java:23: error: ';' expected 
    public SumGenerator(int timesTable, int limit = 10, ArrayList<Integer> previousMultiples) 
                ^
SumGenerator.java:23: error: <identifier> expected 
    public SumGenerator(int timesTable, int limit = 10, ArrayList<Integer> previousMultiples) 
                          ^
5 errors

來源

2013-04-23 James Scholes

這些錯誤是什麼？ – Dancrumb 2013-04-23 20:16:36

http://stackoverflow.com/questions/997482/does-java-support-default-parameter-values – 2013-04-23 20:18:33

您無法提供Java中參數的默認值：int limit = 10。爲了解決問題，提供重載的構造函數。其中一個沒有limit，並且會爲另一個提供默認值。

public SumGenerator(int timesTable, ArrayList<Integer> previousMultiples) 
{ 
    this(timesTable, 10, previousMultiples); 
} 

public SumGenerator(int timesTable, int limit, ArrayList<Integer> previousMultiples) 
{ 
    // Your constructor here. 
}

來源

2013-04-23 20:17:17 rgettman

Java不支持默認參數。

來源

2013-04-23 20:16:56 djechlin

public SumGenerator(int timesTable, int limit = 10, ArrayList<Integer> previousMultiples)

刪除= 10的int limit = 10。 Java不支持構造函數或方法參數的默認值。

來源

2013-04-23 20:17:17 Jesper

使用ArrayList作爲構造函數的參數

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