标签:
* Map接口
*
|-----HashMap:Map的主要实现类
*
|-----LinkedHashMap:使用链表维护添加进Map中的顺序。故遍历Map时,是按添加的顺序遍历的。
*
|-----TreeMap:按照添加进Map中的元素的key的指定属性进行排序。要求:key必须是同一个类的对象!
*
针对key:自然排序 vs
定制排序
*
|-----Hashtable:古老的实现类,线程安全,不建议使用。
*
|----Properties:常用来处理属性文件。键和值都为String类型的
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1 @Test 2 public void test1() { 3 Map map = new HashMap(); 4 map.put("AA", 213); 5 map.put("BB", 456); 6 map.put("BB", 45); 7 map.put(123, "CC"); 8 map.put(null, null); 9 map.put(new Person("DD", 23), 89); 10 map.put(new Person("DD", 23), 87); 11 System.out.println(map.size()); 12 System.out.println(map); 13 map.remove("BB"); 14 System.out.println(map); 15 Object value = map.get(1234); 16 System.out.println(value); 17 }
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1 @Test 2 public void test2() { 3 Map map = new HashMap(); 4 map.put("AA", 213); 5 map.put("BB", 45); 6 map.put(123, "CC"); 7 map.put(null, null); 8 map.put(new Person("DD", 23), 89); 9 10 // 1.遍历key集。 11 Set set = map.keySet(); 12 for (Object obj : set) { 13 System.out.println(obj); 14 } 15 // 2.遍历value集 16 Collection values = map.values(); 17 Iterator i = values.iterator(); 18 while (i.hasNext()) { 19 System.out.println(i.next()); 20 } 21 // 3.如何遍历key-value对。 22 // 方式一: 23 Set set1 = map.keySet(); 24 for (Object obj : set1) { 25 System.out.println(obj + "----->" + map.get(obj)); 26 } 27 // 方式二: 28 Set set2 = map.entrySet(); 29 for (Object obj : set2) { 30 Map.Entry entry = (Map.Entry) obj; 31 // System.out.println(entry.getKey() + "---->" + entry.getValue()); 32 System.out.println(entry); 33 } 34 }
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**LinkedHashMap用法
1 @Test 2 public void test3() { 3 Map map = new LinkedHashMap(); 4 map.put("AA", 213); 5 map.put("BB", 45); 6 map.put(123, "CC"); 7 map.put(null, null); 8 map.put(new Person("DD", 23), 89); 9 10 Set set1 = map.keySet(); 11 for (Object obj : set1) { 12 System.out.println(obj + "----->" + map.get(obj)); 13 } 14 }
1 // 自然排序 2 @Test 3 public void test4() { 4 Map map = new TreeMap(); 5 map.put(new Person("AA", 23), 89); 6 map.put(new Person("MM", 22), 79); 7 map.put(new Person("GG", 23), 99); 8 map.put(new Person("JJ", 13), 69); 9 10 Set set1 = map.keySet(); 11 for (Object obj : set1) { 12 System.out.println(obj + "----->" + map.get(obj)); 13 } 14 }
1 // 定制排序 2 @Test 3 public void test5() { 4 Comparator com = new Comparator() { 5 public int compare(Object o1, Object o2) { 6 if (o1 instanceof Customer && o2 instanceof Customer) { 7 Customer c1 = (Customer) o1; 8 Customer c2 = (Customer) o2; 9 int i = c1.getId().compareTo(c2.getId()); 10 if (i == 0) { 11 return c1.getName().compareTo(c2.getName()); 12 } 13 return i; 14 } 15 return 0; 16 } 17 }; 18 TreeMap map = new TreeMap(com); 19 map.put(new Customer("AA", 1001), 87); 20 map.put(new Customer("CC", 1001), 67); 21 map.put(new Customer("MM", 1004), 77); 22 map.put(new Customer("GG", 1002), 97); 23 24 Set set1 = map.keySet(); 25 for (Object obj : set1) { 26 System.out.println(obj + "----->" + map.get(obj)); 27 } 28 }
-----------------------------------------------------------------------------------以下为填充集合的类
1 class Customer { 2 3 private String name; 4 private Integer id; 5 public String getName() { 6 return name; 7 } 8 public void setName(String name) { 9 this.name = name; 10 } 11 public Integer getId() { 12 return id; 13 } 14 public void setId(Integer id) { 15 this.id = id; 16 } 17 public Customer(String name, Integer id) { 18 super(); 19 this.name = name; 20 this.id = id; 21 } 22 public Customer() { 23 super(); 24 } 25 @Override 26 public String toString() { 27 return "Customer [name=" + name + ", id=" + id + "]"; 28 } 29 @Override 30 public int hashCode() { 31 final int prime = 31; 32 int result = 1; 33 result = prime * result + ((id == null) ? 0 : id.hashCode()); 34 result = prime * result + ((name == null) ? 0 : name.hashCode()); 35 return result; 36 } 37 @Override 38 public boolean equals(Object obj) { 39 if (this == obj) 40 return true; 41 if (obj == null) 42 return false; 43 if (getClass() != obj.getClass()) 44 return false; 45 Customer other = (Customer) obj; 46 if (id == null) { 47 if (other.id != null) 48 return false; 49 } else if (!id.equals(other.id)) 50 return false; 51 if (name == null) { 52 if (other.name != null) 53 return false; 54 } else if (!name.equals(other.name)) 55 return false; 56 return true; 57 } 58 59 } 60 61 class Person implements Comparable{ 62 private String name; 63 private Integer age; 64 public String getName() { 65 return name; 66 } 67 public void setName(String name) { 68 this.name = name; 69 } 70 public Integer getAge() { 71 return age; 72 } 73 public void setAge(Integer age) { 74 this.age = age; 75 } 76 public Person() { 77 super(); 78 } 79 public Person(String name, Integer age) { 80 super(); 81 this.name = name; 82 this.age = age; 83 } 84 @Override 85 public String toString() { 86 return "Person [name=" + name + ", age=" + age + "]"; 87 } 88 //static int init = 1000; 89 @Override 90 public int hashCode() {//return age.hashCode() + name.hashCode();没下述的健壮性好。 91 final int prime = 31; 92 int result = 1; 93 result = prime * result + ((age == null) ? 0 : age.hashCode()); 94 result = prime * result + ((name == null) ? 0 : name.hashCode()); 95 return result; 96 //return init++;//不能这样用 97 } 98 @Override 99 public boolean equals(Object obj) { 100 if (this == obj) 101 return true; 102 if (obj == null) 103 return false; 104 if (getClass() != obj.getClass()) 105 return false; 106 Person other = (Person) obj; 107 if (age == null) { 108 if (other.age != null) 109 return false; 110 } else if (!age.equals(other.age)) 111 return false; 112 if (name == null) { 113 if (other.name != null) 114 return false; 115 } else if (!name.equals(other.name)) 116 return false; 117 return true; 118 } 119 //当向TreeSet中添加Person类的对象时,依据此方法,确定按照哪个属性排列。 120 @Override 121 public int compareTo(Object o) { 122 if(o instanceof Person){ 123 Person p = (Person)o; 124 //return this.name.compareTo(p.name); 125 //return -this.age.compareTo(p.age); 126 int i = this.age.compareTo(p.age); 127 if(i == 0){ 128 return this.name.compareTo(p.name); 129 }else{ 130 return i; 131 } 132 } 133 return 0; 134 } 135 136 }
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原文地址:http://www.cnblogs.com/zhangfan94/p/4263338.html