Java double entry table
Does anyone know a d开发者_JAVA百科ouble entry table implementation in Java I can download ?
I need to do something like this
1 2 3
_______
a| x y z
b| h l m
c| o a k
table.get(a,1)
would return x
Of course, it should use any Object as key, value, etc
There are two basic approaches, depending on your needs.
One is to make a Hashtable
(or similar) of Hashtable
s.
Hashtable<Integer, Hashtable<String, String>> = ...;
Another approach is to build your own datatype that represents an (Integer, String) pair, so you can do:
Hashtable<YourFancyDatatype, String>
The answer to your question partially lies in a previous questions on SO: Java generics Pair<String, String> stored in HashMap not retrieving key->value properly
import java.lang.*;
import java.util.*;
public class Pair<TYPEA, TYPEB> implements Comparable< Pair<TYPEA, TYPEB> > {
protected final TYPEA Key_;
protected final TYPEB Value_;
public Pair(TYPEA key, TYPEB value) {
Key_ = key;
Value_ = value;
}
public TYPEA getKey() {
return Key_;
}
public TYPEB getValue() {
return Value_;
}
public String toString() {
System.out.println("in toString()");
StringBuffer buff = new StringBuffer();
buff.append("Key: ");
buff.append(Key_);
buff.append("\tValue: ");
buff.append(Value_);
return(buff.toString() );
}
public int compareTo( Pair<TYPEA, TYPEB> p1 ) {
System.out.println("in compareTo()");
if ( null != p1 ) {
if ( p1.equals(this) ) {
return 0;
} else if ( p1.hashCode() > this.hashCode() ) {
return 1;
} else if ( p1.hashCode() < this.hashCode() ) {
return -1;
}
}
return(-1);
}
public int hashCode() {
int hashCode = Key_.hashCode() + (31 * Value_.hashCode());
System.out.println("in hashCode() [" + Integer.toString(hashCode) + "]");
return(hashCode);
}
@Override
public boolean equals(Object o) {
System.out.println("in equals()");
if (o instanceof Pair) {
Pair<?, ?> p1 = (Pair<?, ?>) o;
if ( p1.Key_.equals( this.Key_ ) && p1.Value_.equals( this.Value_ ) ) {
return(true);
}
}
return(false);
}
public static void main(String [] args) {
HashMap< Pair<String, int>, String> table = new HashMap<Pair<String,int>, String>();
table.put(new Pair<String, int>("a", 1), "x");
table.put(new Pair<String, int>("a", 2), "y");
table.put(new Pair<String, int>("a", 3), "z");
table.put(new Pair<String, int>("b", 1), "h");
table.put(new Pair<String, int>("b", 2), "l");
table.put(new Pair<String, int>("b", 3), "m");
table.put(new Pair<String, int>("c", 1), "o");
table.put(new Pair<String, int>("c", 2), "a");
table.put(new Pair<String, int>("c", 3), "k");
String val = table.get(new Pair<String, int>("a", 1)); //val is x for this input pair
}
}
I'm assuming you have an array of characters/objects and a quantity and want cross each other in your table. You could map each character to a number between 0 .. qtyOfCharacters and simply create a bidimensional array Object[][] table = new Object[A][B], where A is the quantity of characters/object just mapped, and B is the quantity of columns.
To map the characters/object to numbers you should use a HashMap/HashTable.
The idea is that if you access the element at "a,3" you should write table[ charmap.get("a")][ 3]
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