Map

1）map的key采用简单形式和复杂形式时，查找的效率是不同的，简单的key值效率更高
2）当数据量大的时候，采用entrySet遍历key+value的效率要高于keySet
3）当我们只需要取得value值时，采用values来遍历效率更高

遍历key/value

  1. Iterator<String> iter = map.keySet().iterator();
  2. while (iter.hasNext()){
  3. key=iter.next();
  4. value=map.get(key);
  5. }
  7. for(String key2:map.keySet()){
  8. value=map.get(key2);
  9. }
  11. Iterator<Map.Entry<String,String>> iter3 =map.entrySet().iterator();
  12. Map.Entry<String,String> entry3;
  13. while (iter3.hasNext()){
  14. entry3 = iter3.next();
  15. key = entry3.getKey();
  16. value=entry3.getValue();
  17. }
  19. for(Map.Entry<String,String> entry4:map.entrySet()){
  20. key=entry4.getKey();
  21. value=entry4.getValue();
  22. }
  24. Iterator<String> iter = map.keySet().iterator();
  25. while (iter.hasNext()){
  26. key=iter.next();
  27. }
  29. for(String key2:map.keySet()){
  31. }
  33. Iterator<Map.Entry<String,String>> iter3 =map.entrySet().iterator();
  34. Map.Entry<String,String> entry3;
  35. while (iter3.hasNext()){
  36. key = iter3.next().getKey();
  38. }
  40. for(Map.Entry<String,String> entry4:map.entrySet()){
  41. key=entry4.getKey();
  42. }
  44. Iterator<String> iter = map.keySet().iterator();
  45. while (iter.hasNext()){
  46. value=map.get(iter.next());
  47. }
  49. for(String key2:map.keySet()){
  50. value=map.get(key2);
  51. }
  53. Iterator<Map.Entry<String,String>> iter3 =map.entrySet().iterator();
  54. Map.Entry<String,String> entry3;
  55. while (iter3.hasNext()){
  56. value=iter3.next().getValue();
  58. }
  60. for(Map.Entry<String,String> entry4:map.entrySet()){
  61. value=entry4.getValue();
  62. }
  64. Iterator<String>  iter5=map.values().iterator();
  65. while (iter5.hasNext()){
  66. value=iter5.next();
  67. }
  69. for(String value6:map.values()){
  71. }