Java: If vs. Switch
Ich habe ein Stück Code mit a), das ich aus Gründen der Lesbarkeit durch b) ersetzt habe ...
ein)
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;
}
BEARBEITEN:
Einige der nachstehenden Antworten beziehen sich auf alternative Ansätze zu dem oben genannten Ansatz.
Ich habe das Folgende eingefügt, um den Kontext für seine Verwendung bereitzustellen.
Der Grund, warum ich die Frage oben gestellt habe, war, dass sich die Geschwindigkeit des empirischen Hinzufügens von Wörtern verbessert hat.
Dies ist keineswegs Produktionscode und wurde schnell als PoC zusammen gehackt.
Das Folgende scheint eine Bestätigung des Scheiterns eines Gedankenexperiments zu sein.
Möglicherweise benötige ich einen viel größeren Wortschatz als den, den ich derzeit verwende.
Der Fehler ergibt sich aus der Tatsache, dass ich die Nullreferenzen, die noch Speicher benötigen, nicht berücksichtigt habe. (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 );
}
}