1，字符串次数的统计：

计算同一个人出现在一个地方的次数；

  1. package day08.Demo01;
  3. import java.util.ArrayList;
  4. import java.util.HashMap;
  5. import java.util.Map;
  6. import java.util.Set;
  8. /**
  9.  * @author Jztice5
  10.  * @date 2022年02月15日 8:56
  11.  */
  13. public class Text02 {
  14. //
  15. //    小婷,广州
  16. //            武武,广州
  17. //    武武,深圳
  18. //            武武,东莞
  19. //    小婷,广州
  20. //            小婷,深圳
  21. //    武武,东莞
  22. //            武武,东莞
  23.     public static void main(String[] args) {
  24.         A a1 = new A("小婷", "广州");
  25.         A a2 = new A("武武", "广州");
  26.         A a3 = new A("武武", "深圳");
  27.         A a4 = new A("武武", "东莞");
  28.         A a5 = new A("小婷", "广州");
  29.         A a6 = new A("小婷", "深圳");
  30.         A a7 = new A("武武", "东莞");
  31.         A a8 = new A("武武", "东莞");
  33.         ArrayList<A> list = new ArrayList<>();
  34.         list.add(a1);
  35.         list.add(a2);
  36.         list.add(a3);
  37.         list.add(a4);
  38.         list.add(a5);
  39.         list.add(a6);
  40.         list.add(a7);
  41.         list.add(a8);
  43.         HashMap<A, Integer> map1 = new HashMap<>();
  44.         for (A a : list) {
  45.             if (map1.containsKey(a)){
  46. //                Set<Map.Entry<String, Integer>> entrySet = map1.entrySet();
  48.                 // ！！！一定要注意，去重就要重写equals和hashcode
  49.                 map1.put(a,map1.get(a)+1);
  50.             }else {
  51.                 map1.put(a,1);
  52.             }
  53.         }
  55.         Set<Map.Entry<A, Integer>> entrySet = map1.entrySet();
  56.         for (Map.Entry<A, Integer> entry : entrySet) {
  57.             A key = entry.getKey();
  58.             Integer value = entry.getValue();
  59.             System.out.println(key+"\t"+value);
  60.         }
  61.     }
  63. }
  64. class A{
  65.     private String name;
  66.     private String address;
  68.     public A() {
  69.     }
  71.     public A(String name, String address) {
  72.         this.name = name;
  73.         this.address = address;
  74.     }
  76.     /**
  77.      * 获取
  78.      * @return name
  79.      */
  80.     public String getName() {
  81.         return name;
  82.     }
  84.     /**
  85.      * 设置
  86.      * @param name
  87.      */
  88.     public void setName(String name) {
  89.         this.name = name;
  90.     }
  92.     /**
  93.      * 获取
  94.      * @return address
  95.      */
  96.     public String getAddress() {
  97.         return address;
  98.     }
  100.     /**
  101.      * 设置
  102.      * @param address
  103.      */
  104.     public void setAddress(String address) {
  105.         this.address = address;
  106.     }
  108.     public String toString() {
  109.         return "A{name = " + name + ", address = " + address + "}";
  110.     }
  112.     //去重！！！！！！！！！！！！！！！
  113.     @Override
  114.     public boolean equals(Object o) {
  115.         if (this == o) return true;
  116.         if (o == null || getClass() != o.getClass()) return false;
  118.         A a = (A) o;
  120.         if (name != null ? !name.equals(a.name) : a.name != null) return false;
  121.         return address != null ? address.equals(a.address) : a.address == null;
  122.     }
  124.     @Override
  125.     public int hashCode() {
  126.         int result = name != null ? name.hashCode() : 0;
  127.         result = 31 * result + (address != null ? address.hashCode() : 0);
  128.         return result;
  129.     }
  130. }