ArrayList和java.lang.OutOfMemoryError

user3396201 发表于 Dev

用户3396201

我正在尝试使程序创建ArrayList初始大小为1并用随机数填充它。接下来，ArrayList清除，将的大小ArrayList增加1，然后再次填充随机数。我希望程序重复这些步骤，直到ArrayList大小等于用户指定的数字为止。

因此，输出将例如：

1个

3,8

6,3,7

...

ñ

到目前为止，我已经制作了：

public static void main (String args[]){
    
    ArrayList<Integer> al = new ArrayList<Integer>(); 
    Random rand = new Random();
    int val=1;
    int ii =1;
    while(val<400){
    for (int j = 0; j<ii;)
    {
        ii++;
        val++;
        pick = rand.nextInt(100);
        al.add(pick);
    }

    System.out.println("Contents of al: " + al);

    al.clear();
    System.out.print("Array has been cleared: " + al);
}

有什么想法如何使其工作吗？

bspencer

您永远不会增加j。您正在for循环内增加ii和val，正如我认为您实际上想要在while循环中进行的那样。请尝试下面的示例。

    ArrayList<Integer> al = new ArrayList<Integer>(); 
    Random rand = new Random();
    int val=1;
    int ii =0;
    while(val < 400){
        for (int j = 0; j<ii; j++) {
            int pick = rand.nextInt(100);
            al.add(pick);
        }
        ii++;
        val++;
        System.out.println("Contents of al: " + al);
        al.clear();
        System.out.print("Array has been cleared: " + al);
    }

如果给变量赋予有意义的名称，您的任务将容易得多。例如

    ArrayList<Integer> al = new ArrayList<Integer>(); 
    Random rand = new Random();
    int lineNumber = 1;
    int lineLength = 0;
    while(lineNumber < 400){
        for (int randCount = 0; randCount < lineLength; randCount++) {
            int pick = rand.nextInt(100);
            al.add(pick);
        }
        lineLength++;
        lineNumber++;
        System.out.println("Contents of al: " + al);
        al.clear();
        System.out.print("Array has been cleared: " + al);
    }