使用ArrayList作为构造函数的参数

-1

我想写一个接受ArrayList（包含整数）作为其参数之一的类的构造函数。稍后再实例化这个类时，我会传递一个适当的，预先填充的值列表，所以我不想在构造函数中创建一个空列表。使用ArrayList作为构造函数的参数

不幸的是，当我尝试编译下面的代码时，Java吐出了五个错误，都与第23行（我的构造函数的定义）有关。任何意见将不胜感激：

/* 
* 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

来源

2013-04-23 James Scholes

这些错误是什么？ – Dancrumb 2013-04-23 20:16:36

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

您无法提供Java中参数的默认值：int limit = 10。为了解决问题，提供重载的构造函数。其中一个没有limit，并且会为另一个提供默认值。

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

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

来源

2013-04-23 20:17:17 rgettman

Java不支持默认参数。

来源

2013-04-23 20:16:56 djechlin

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

删除= 10的int limit = 10。 Java不支持构造函数或方法参数的默认值。

来源

2013-04-23 20:17:17 Jesper

使用ArrayList作为构造函数的参数

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