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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6.  
  7. /* Name of the class has to be "Main" only if the class is public. */
  8. class Ideone
  9. {
  10. 	public static void main (String[] args) throws java.lang.Exception
  11. 	{
  12.  
  13. 		// start - create two arraylist which contains map in it.
  14. 		List<HashMap<String, String>> a1 = new ArrayList<HashMap<String, String>>();
  15. 		HashMap<String, String> m1 = new HashMap<String, String>();
  16. 		HashMap<String, String> m2 = new HashMap<String, String>();
  17. 		HashMap<String, String> m3 = new HashMap<String, String>();
  18. 		HashMap<String, String> m4 = new HashMap<String, String>();
  19. 		m1.put("1", "19");
  20. 		m2.put("2", "22");
  21. 		m3.put("3", "2");
  22. 		m4.put("4", "49");
  23. 		a1.add(m1);
  24. 		a1.add(m2);
  25. 		a1.add(m3);
  26. 		a1.add(m4);
  27. 		List<HashMap<String, String>> a2 = new ArrayList<HashMap<String, String>>();
  28. 		HashMap<String, String> m5 = new HashMap<String, String>();
  29. 		HashMap<String, String> m6 = new HashMap<String, String>();
  30. 		HashMap<String, String> m7 = new HashMap<String, String>();
  31. 		HashMap<String, String> m8 = new HashMap<String, String>();
  32. 		m5.put("1", "12");
  33. 		m6.put("2", "22");
  34. 		m7.put("3", "32");
  35. 		m8.put("5", "52");
  36. 		a2.add(m5);
  37. 		a2.add(m6);
  38. 		a2.add(m7);
  39. 		a2.add(m8);
  40. 		// end - create two arraylist which contains map in it.
  41.  
  42. 		int i = 0, j = 0;
  43.  
  44. 		// start- get arrayList a1 index entries, fetch map,put all maps into one map to remove
  45. 		// duplicate keys,doesn't matter value- because they will be removed anyways)
  46. 		Map<String, String> lOld = new HashMap<String, String>();
  47. 		for (i = 0; i < a1.size(); i++) {
  48. 			HashMap<String, String> a1Map = a1.get(i);
  49. 			lOld.putAll(a1Map);
  50. 		}
  51. 		//end
  52.  
  53. 		// start- get arrayList a2 index entries, fetch map,put all maps into other map to remove
  54. 		// duplicate keys,doesn't matter value- because they will be removed anyways)
  55.  
  56. 		HashMap<String, String> lNew = new HashMap<String, String>();
  57. 		for (j = 0; j < a2.size(); j++) {
  58. 			HashMap<String, String> a2Map = a2.get(j);
  59. 			lNew.putAll(a2Map);
  60. 		}
  61.  
  62. 		// check if first map keys (set) is in second map keys (set). if yes, add them into a list.
  63. 		List<String> toRemove = new ArrayList<>();
  64. 		Set<String> oldKeys = lOld.keySet();
  65. 		Set<String> newKeys = lNew.keySet();
  66. 		for (String oldKey : oldKeys) {
  67. 			if (lNew.containsKey(oldKey)) {
  68. 				toRemove.add(oldKey);
  69. 			}
  70. 		}
  71.  
  72. 		// remove that list elements from both sets which will remove them from map itself.
  73. 		oldKeys.removeAll(toRemove);
  74. 		newKeys.removeAll(toRemove);
  75.  
  76. 		// print both map
  77. 		System.out.println("lold map is: " + lOld);
  78. 		System.out.println("lNew map is: " + lNew);
  79.  
  80. 		// don't remove elements froms et while iterating. it will give ConcurrentModificationException
  81. 	}
  82. }
Success #stdin #stdout 0.05s 2184192KB
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Standard input is empty
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lold map is: {4=49}
lNew map is: {5=52}
https://ideone.com/FTDhYM
language:
Java (HotSpot 12)
created:
5 years ago
visibility:
public

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