Merge Intervals LeetCode solution in Java

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class Solution {
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  public int[][] merge(int[][] intervals) {
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    // sort
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    // unknown size of ans = use ArrayList
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    // insert from back
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    // case 1 : Merging
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    // start of new interval is less that end of old interval
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    // new end = Math.max(new intervals end, old intervals end)
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    // case 2 : Non-merging
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    // seperate interval
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    // convert ArrayList to array and return
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    Arrays.sort(intervals, (a, b) -> a[0] - b[0]);
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    ArrayList<int[]> list = new ArrayList<>();
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    for (int i = 0; i < intervals.length; i++) {
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      if (i == 0) {
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        list.add(intervals[i]);
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      } else {
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        int[] prev = list.get(list.size() - 1);
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        int[] curr = intervals[i];
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        if (curr[0] <= prev[1]) {
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          prev[1] = Math.max(curr[1], prev[1]);
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        } else {
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          list.add(curr);
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        }
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      }
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    }
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    return list.toArray(new int[list.size()][2]);
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  }
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}