[英]HeapSpace requirement in java - Arrays.sort() vs Collections.sort()
I have written a method which sorts the arrayList and them swaps the consecutive elements in that arrayList. 我已经编写了一种对arrayList进行排序的方法,它们交换该arrayList中的连续元素。 I am facing a issue -
我面临一个问题-
If I implement the method by using Collections.sort() it gives heapsize error while if I use Arrays.sort() it does not and run successfully. 如果我使用Collections.sort()实现该方法,则会产生堆大小错误,而如果我使用Arrays.sort(),则不会并成功运行。
public ArrayList<Integer> sortAndSwap(ArrayList<Integer> a) {
Collections.sort(a);
for(int i = 0; i < a.size()-1; i+=2) {
int temp = a.get(i);
a.add(i, a.get(i+1));
a.add(i+1, temp);
}
return a;
}
this method gives the below error - 此方法出现以下错误-
Exception in thread "main" java.lang.OutOfMemoryError: Java heap space at java.util.Arrays.copyOf(Arrays.java:3210) at java.util.Arrays.copyOf(Arrays.java:3181) at java.util.ArrayList.grow(ArrayList.java:261) at java.util.ArrayList.ensureExplicitCapacity(ArrayList.java:235) at java.util.ArrayList.ensureCapacityInternal(ArrayList.java:227) at java.util.ArrayList.add(ArrayList.java:475) at Solution.wave(Solution.java:7) at Main.main(Main.java:322)
线程“主”中的异常java.lang.OutOfMemoryError:java.util.Arrays.copyOf(Arrays.java:3181)处的java.util.Arrays.copyOf(Arrays.java:3210)处的Java堆空间。 ArrayList.grow(ArrayList.java:261)at java.util.ArrayList.ensureExplicitCapacity(ArrayList.java:235)at java.util.ArrayList.ensureCapacityInternal(ArrayList.java:227)at java.util.ArrayList.add(ArrayList) .java:475)在Main.main(Main.java:322)的Solution.wave(Solution.java:7)
while if i modify it as follows 而如果我如下修改
public ArrayList<Integer> sortAndSwap(ArrayList<Integer> a) {
Integer []arr = new Integer[a.size()];
a.toArray(arr);
Arrays.sort(arr);
for(int i = 0; i < a.size()-1; i+=2) {
int temp = arr[i];
arr[i] = arr[i+1];
arr[i+1] = temp;
}
a = new ArrayList<Integer>(Arrays.asList(arr));
return a;
}
It runs fine and gives desired results. 它运行良好,并提供所需的结果。 Why is this happening, can anybody explain ?
为什么会这样,有人可以解释吗? Thanks !
谢谢 !
For the swap operation you call add
when you should use set
. 对于交换操作,应在使用
set
时调用add
。 So you are increasing the list endlessly. 因此,您正在不断增加清单。
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