Merge Two Sorted Lists LeetCode solution in Java

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class Solution {
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  public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
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    if (list1 == null && list2 == null) return null;
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    if (list1 == null) return list2;
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    if (list2 == null) return list1;
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    ListNode newHead = new ListNode();
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    ListNode newNode = newHead;
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    while (list1 != null && list2 != null) {
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      // ListNode newNode = new ListNode();
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      if (list1.val <= list2.val) {
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        newNode.next = list1;
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        list1 = list1.next;
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      } else if (list1.val >= list2.val) {
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        newNode.next = list2;
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        list2 = list2.next;
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      }
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      newNode = newNode.next;
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    }
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    if (list1 != null) newNode.next = list1;
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    else if (list2 != null) newNode.next = list2;
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    return newHead.next;
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  }
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}