java guava Table、HashBasedTable、TreeBasedTable记录

在实际工作中，如果我们想用索引数据结构的时候，我相信大多数人会使用 Map嵌套Map的数据结构，如 Map>，这种Map套Map数据结构，操作起来很繁琐的。

由rowkey + columnKey 为索引，存储 value的。

    com.google.guava
    guava
    19.0

import java.util.Map;
import java.util.Set;

import com.google.common.collect.HashBasedTable;
import com.google.common.collect.Table;

public class GuavaTester {

   public static void main(String args[]){
      //create a table
      Table employeeTable = HashBasedTable.create();

      //initialize the table with employee details
      employeeTable.put("IBM", "101","Mahesh");
      employeeTable.put("IBM", "102","Ramesh");
      employeeTable.put("IBM", "103","Suresh");

      employeeTable.put("Microsoft", "111","Sohan");
      employeeTable.put("Microsoft", "112","Mohan");
      employeeTable.put("Microsoft", "113","Rohan");

      employeeTable.put("TCS", "121","Ram");
      employeeTable.put("TCS", "122","Shyam");
      employeeTable.put("TCS", "123","Sunil");

      //get Map corresponding to IBM
      Map ibmEmployees =  employeeTable.row("IBM");

      System.out.println("List of IBM Employees");
      for(Map.Entry entry : ibmEmployees.entrySet()){
         System.out.println("Emp Id: " + entry.getKey() + ", Name: " + entry.getValue());
      }

      //get all the unique keys of the table
      Set employers = employeeTable.rowKeySet();
      System.out.print("Employers: ");
      for(String employer: employers){
         System.out.print(employer + " ");
      }
      System.out.println();

      //get a Map corresponding to 102
      Map EmployerMap =  employeeTable.column("102");
      for(Map.Entry entry : EmployerMap.entrySet()){
         System.out.println("Employer: " + entry.getKey() + ", Name: " + entry.getValue());
      }		
   }	
}
//更多请阅读：https://www.yiibai.com/guava/guava_table.html

运行结果：

List of IBM Employees
Emp Id: 102, Name: Ramesh
Emp Id: 101, Name: Mahesh
Emp Id: 103, Name: Suresh

Employers: IBM TCS Microsoft
Employer: IBM, Name: Ramesh

HashBasedTable：基于HashMap>的实现。
TreeBasedTable：基于TreeMap>的实现。
ImmutableTable：基于ImmutableMap>的实现。