Java: If vs. Switch
- by _ande_turner_
I have a piece of code with a) which I replaced with b) purely for legibility ...
a)
if ( WORD[ INDEX ] == 'A' ) branch = BRANCH.A;
/* B through to Y */
if ( WORD[ INDEX ] == 'Z' ) branch = BRANCH.Z;
b)
switch ( WORD[ INDEX ] ) {
case 'A' : branch = BRANCH.A; break;
/* B through to Y */
case 'Z' : branch = BRANCH.Z; break;
}
... will the switch version cascade through all the permutations or jump to a case ?
EDIT:
Some of the answers below regard alternative approaches to the approach above.
I have included the following to provide context for its use.
The reason I asked, the Question above, was because the speed of adding words empirically improved.
This isn't production code by any means, and was hacked together quickly as a PoC.
The following seems to be a confirmation of failure for a thought experiment.
I may need a much bigger corpus of words than the one I am currently using though.
The failure arises from the fact I did not account for the null references still requiring memory. ( doh ! )
public class Dictionary {
private static Dictionary ROOT;
private boolean terminus;
private Dictionary A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z;
private static Dictionary instantiate( final Dictionary DICTIONARY ) {
return ( DICTIONARY == null ) ? new Dictionary() : DICTIONARY;
}
private Dictionary() {
this.terminus = false;
this.A = this.B = this.C = this.D = this.E = this.F = this.G = this.H = this.I = this.J = this.K = this.L = this.M = this.N = this.O = this.P = this.Q = this.R = this.S = this.T = this.U = this.V = this.W = this.X = this.Y = this.Z = null;
}
public static void add( final String...STRINGS ) {
Dictionary.ROOT = Dictionary.instantiate( Dictionary.ROOT );
for ( final String STRING : STRINGS ) Dictionary.add( STRING.toUpperCase().toCharArray(), Dictionary.ROOT , 0, STRING.length() - 1 );
}
private static void add( final char[] WORD, final Dictionary BRANCH, final int INDEX, final int INDEX_LIMIT ) {
Dictionary branch = null;
switch ( WORD[ INDEX ] ) {
case 'A' : branch = BRANCH.A = Dictionary.instantiate( BRANCH.A ); break;
case 'B' : branch = BRANCH.B = Dictionary.instantiate( BRANCH.B ); break;
case 'C' : branch = BRANCH.C = Dictionary.instantiate( BRANCH.C ); break;
case 'D' : branch = BRANCH.D = Dictionary.instantiate( BRANCH.D ); break;
case 'E' : branch = BRANCH.E = Dictionary.instantiate( BRANCH.E ); break;
case 'F' : branch = BRANCH.F = Dictionary.instantiate( BRANCH.F ); break;
case 'G' : branch = BRANCH.G = Dictionary.instantiate( BRANCH.G ); break;
case 'H' : branch = BRANCH.H = Dictionary.instantiate( BRANCH.H ); break;
case 'I' : branch = BRANCH.I = Dictionary.instantiate( BRANCH.I ); break;
case 'J' : branch = BRANCH.J = Dictionary.instantiate( BRANCH.J ); break;
case 'K' : branch = BRANCH.K = Dictionary.instantiate( BRANCH.K ); break;
case 'L' : branch = BRANCH.L = Dictionary.instantiate( BRANCH.L ); break;
case 'M' : branch = BRANCH.M = Dictionary.instantiate( BRANCH.M ); break;
case 'N' : branch = BRANCH.N = Dictionary.instantiate( BRANCH.N ); break;
case 'O' : branch = BRANCH.O = Dictionary.instantiate( BRANCH.O ); break;
case 'P' : branch = BRANCH.P = Dictionary.instantiate( BRANCH.P ); break;
case 'Q' : branch = BRANCH.Q = Dictionary.instantiate( BRANCH.Q ); break;
case 'R' : branch = BRANCH.R = Dictionary.instantiate( BRANCH.R ); break;
case 'S' : branch = BRANCH.S = Dictionary.instantiate( BRANCH.S ); break;
case 'T' : branch = BRANCH.T = Dictionary.instantiate( BRANCH.T ); break;
case 'U' : branch = BRANCH.U = Dictionary.instantiate( BRANCH.U ); break;
case 'V' : branch = BRANCH.V = Dictionary.instantiate( BRANCH.V ); break;
case 'W' : branch = BRANCH.W = Dictionary.instantiate( BRANCH.W ); break;
case 'X' : branch = BRANCH.X = Dictionary.instantiate( BRANCH.X ); break;
case 'Y' : branch = BRANCH.Y = Dictionary.instantiate( BRANCH.Y ); break;
case 'Z' : branch = BRANCH.Z = Dictionary.instantiate( BRANCH.Z ); break;
}
if ( INDEX == INDEX_LIMIT ) branch.terminus = true;
else Dictionary.add( WORD, branch, INDEX + 1, INDEX_LIMIT );
}
public static boolean is( final String STRING ) {
Dictionary.ROOT = Dictionary.instantiate( Dictionary.ROOT );
return Dictionary.is( STRING.toUpperCase().toCharArray(), Dictionary.ROOT, 0, STRING.length() - 1 );
}
private static boolean is( final char[] WORD, final Dictionary BRANCH, final int INDEX, final int INDEX_LIMIT ) {
Dictionary branch = null;
switch ( WORD[ INDEX ] ) {
case 'A' : branch = BRANCH.A; break;
case 'B' : branch = BRANCH.B; break;
case 'C' : branch = BRANCH.C; break;
case 'D' : branch = BRANCH.D; break;
case 'E' : branch = BRANCH.E; break;
case 'F' : branch = BRANCH.F; break;
case 'G' : branch = BRANCH.G; break;
case 'H' : branch = BRANCH.H; break;
case 'I' : branch = BRANCH.I; break;
case 'J' : branch = BRANCH.J; break;
case 'K' : branch = BRANCH.K; break;
case 'L' : branch = BRANCH.L; break;
case 'M' : branch = BRANCH.M; break;
case 'N' : branch = BRANCH.N; break;
case 'O' : branch = BRANCH.O; break;
case 'P' : branch = BRANCH.P; break;
case 'Q' : branch = BRANCH.Q; break;
case 'R' : branch = BRANCH.R; break;
case 'S' : branch = BRANCH.S; break;
case 'T' : branch = BRANCH.T; break;
case 'U' : branch = BRANCH.U; break;
case 'V' : branch = BRANCH.V; break;
case 'W' : branch = BRANCH.W; break;
case 'X' : branch = BRANCH.X; break;
case 'Y' : branch = BRANCH.Y; break;
case 'Z' : branch = BRANCH.Z; break;
}
if ( branch == null ) return false;
if ( INDEX == INDEX_LIMIT ) return branch.terminus;
else return Dictionary.is( WORD, branch, INDEX + 1, INDEX_LIMIT );
}
}
