Java：枚举与if-then-else的性能

是的，是的，因为一般而言，switch语句的运行速度比if / else链更快。

尽管生成的字节码并非始终是性能比较的权威来源，但是您可以检查一下它是否有更好的主意。

例如此代码：

class A {     enum N { ONE, TWO, THREE }    void testSwitch( N e ) {         switch( e ) {  case ONE : x(); break; case TWO : x(); break; case THREE : x(); break;        }    }    void testIf( Enum e ) {         if( e == N.ONE ) { x(); }        else if( e == N.TWO ) { x(); }        else if( e == N.THREE ) { x(); }    }    void x(){}}

生成以下内容：

Compiled from "A.java"class A extends java.lang.Object{A();  Code:   0:   aload_0   1:   invokespecial   #1; //Method java/lang/Object."<init>":()V   4:   returnvoid testSwitch(A$N);  Code:   0:   getstatic   #2; //Field A$1.$SwitchMap$A$N:[I   3:   aload_1   4:   invokevirtual   #3; //Method A$N.ordinal:()I   7:   iaload   8:   tableswitch{ //1 to 3        1: 36;        2: 43;        3: 50;        default: 54 }   36:  aload_0   37:  invokevirtual   #4; //Method x:()V   40:  goto    54   43:  aload_0   44:  invokevirtual   #4; //Method x:()V   47:  goto    54   50:  aload_0   51:  invokevirtual   #4; //Method x:()V   54:  returnvoid testIf(java.lang.Enum);  Code:   0:   aload_1   1:   getstatic   #5; //Field A$N.ONE:LA$N;   4:   if_acmpne   14   7:   aload_0   8:   invokevirtual   #4; //Method x:()V   11:  goto    39   14:  aload_1   15:  getstatic   #6; //Field A$N.TWO:LA$N;   18:  if_acmpne   28   21:  aload_0   22:  invokevirtual   #4; //Method x:()V   25:  goto    39   28:  aload_1   29:  getstatic   #7; //Field A$N.THREE:LA$N;   32:  if_acmpne   39   35:  aload_0   36:  invokevirtual   #4; //Method x:()V   39:  returnvoid x();  Code:   0:   return}

在两种情况下，这似乎都非常快。

因此，选择一种易于维护的工具。