Question

I am using multiple hashtables for a program viz table1 table2 table3 etc. Each table has 3 key-value pairs. the keys are same with different values.
Now in the UI of my program i have a comobobox to pick the table name from user. Once it is selected i am storing it in a variable and would like to use this variable to open the appropriate table.

Thanks Eric Coolman for this piece which i have edited here for my query.

Hashtable table1 = new Hashtable();

table1 .put("COL1", Double.toString(dvalue1));
table1 .put("COL2", value2);
table1 .put("COL3", value3);

Hashtable table2 = new Hashtable();

table2 .put("COL1", Double.toString(dvalue4));
table2 .put("COL2", value5);
table2 .put("COL3", value6);

// reading that value back:

double dvalue1 = Double.parseDouble((String)table1.get("COL1"));
double value6= Double.parseDouble((String)table2.get("COL3"));`

here how can i use a variable instead of table1 and table2? what is the syntax. I am new to java.

Answer 1

First of, your structure looks like you are in object denial: what you’ve got as Hashtable object should probably be objects of a custom type with 3 fields (col1, col2 and col3; or more readable versions of that).

Next: you can simply use a third variable to switch on which object you read from:

Hashtable readFromMe;
if (someCondition)
  readFromMe=table1;
else
  readFromMe=table2;

Object o = readFromMe.get("COL3");

This code would read from table1 if someCondition is true and from table2 otherwise.

Also, a shorter version of the first 5 lines of the code above would be Hashtable readFromMe = someCondition ? table1 : table2;.