現在你有這種方式,你有兩個寫NxN if
語句爲每個類別有N個單位。
if from_spinner is Degree
if to_spinner is Degree
return input
if to_spinner is Radian
return input * 0.0174532925199
if to_spinner is Gradian
return input * 1.11111111111
if from_spinner is Radian
if to_spinner is Degree
return input * 57.2957795131
if to_spinner is Radian
return input
if to_spinner is Gradian
return input * 63.6619772368
if from_spinner is Gradian
if to_spinner is Degree
return input * 0.9
if to_spinner is Radian
return input * 0.0157079632679
if to_spinner is Gradian
return input
取而代之的是,選擇一個單元作爲輸入和輸出之間的中介。然後您需要輸入N if
語句將輸入轉換爲中介,並將N if
語句從中間轉換爲輸出,總計爲2N。
//we will use degrees as the intermediary unit
intermediary = null
//caluclate intermediary
if from_spinner is Degree
intermediary = input
if from_spinner is Radian
intermediary = input * 57.2957795131
if from_spinner is Gradian
intermediary = input * 0.9
//calculate final
if to_spinner is Degree
return intermediary
if to_spinner is Radian
return intermediary/57.2957795131
if to_spinner is Gradian
return intermediary/0.9
當你只有三個單位時,看起來效率並不高,但是對於較大的N值,它可以節省你很多的努力。例如,將此105行雙重嵌套方法與其使用中間值的29行等效值進行比較:
if from_spinner is Millimeter
if to_spinner is Millimeter
return input
if to_spinner is Centimeter
return input * 0.1
if to_spinner is Meter
return input * 0.001
if to_spinner is Kilometer
return input * 1e-06
if to_spinner is Inch
return input * 0.0393700787402
if to_spinner is Foot
return input * 0.00328083989501
if to_spinner is Mile
return input * 6.2137273665e-07
if from_spinner is Centimeter
if to_spinner is Millimeter
return input * 10.0
if to_spinner is Centimeter
return input
if to_spinner is Meter
return input * 0.01
if to_spinner is Kilometer
return input * 1e-05
if to_spinner is Inch
return input * 0.393700787402
if to_spinner is Foot
return input * 0.0328083989501
if to_spinner is Mile
return input * 6.2137273665e-06
if from_spinner is Meter
if to_spinner is Millimeter
return input * 1000.0
if to_spinner is Centimeter
return input * 100.0
if to_spinner is Meter
return input
if to_spinner is Kilometer
return input * 0.001
if to_spinner is Inch
return input * 39.3700787402
if to_spinner is Foot
return input * 3.28083989501
if to_spinner is Mile
return input * 0.00062137273665
if from_spinner is Kilometer
if to_spinner is Millimeter
return input * 1000000.0
if to_spinner is Centimeter
return input * 100000.0
if to_spinner is Meter
return input * 1000.0
if to_spinner is Kilometer
return input
if to_spinner is Inch
return input * 39370.0787402
if to_spinner is Foot
return input * 3280.83989501
if to_spinner is Mile
return input * 0.62137273665
if from_spinner is Inch
if to_spinner is Millimeter
return input * 25.4
if to_spinner is Centimeter
return input * 2.54
if to_spinner is Meter
return input * 0.0254
if to_spinner is Kilometer
return input * 2.54e-05
if to_spinner is Inch
return input
if to_spinner is Foot
return input * 0.0833333333333
if to_spinner is Mile
return input * 1.57828675109e-05
if from_spinner is Foot
if to_spinner is Millimeter
return input * 304.8
if to_spinner is Centimeter
return input * 30.48
if to_spinner is Meter
return input * 0.3048
if to_spinner is Kilometer
return input * 0.0003048
if to_spinner is Inch
return input * 12.0
if to_spinner is Foot
return input
if to_spinner is Mile
return input * 0.000189394410131
if from_spinner is Mile
if to_spinner is Millimeter
return input * 1609340.0
if to_spinner is Centimeter
return input * 160934.0
if to_spinner is Meter
return input * 1609.34
if to_spinner is Kilometer
return input * 1.60934
if to_spinner is Inch
return input * 63359.8425197
if to_spinner is Foot
return input * 5279.98687664
if to_spinner is Mile
return input
。
intermediary = null
if from_spinner is Millimeter
intermediary = input * 0.001
if from_spinner is Centimeter
intermediary = input * 0.01
if from_spinner is Meter
intermediary = input * 1.0
if from_spinner is Kilometer
intermediary = input * 1000.0
if from_spinner is Inch
intermediary = input * 0.0254
if from_spinner is Foot
intermediary = input * 0.3048
if from_spinner is Mile
intermediary = input * 1609.34
if to_spinner is Millimeter
return intermediary/0.001
if to_spinner is Centimeter
return intermediary/0.01
if to_spinner is Meter
return intermediary/1.0
if to_spinner is Kilometer
return intermediary/1000.0
if to_spinner is Inch
return intermediary/0.0254
if to_spinner is Foot
return intermediary/0.3048
if to_spinner is Mile
return intermediary/1609.34
可以請您詳細說明嗎?有三個變量。打開什麼? –
看到這個例子,你可以只打開整型常量(僅限Strings,Java 7+,在android上不可用)。 – dst
在你的特殊情況下,你可以首先在值類型上做一個switch語句,然後在每個case block內部依次執行兩個例子:首先將to_value賦給你選擇的任何單位(常量),然後將結果帶到目標值。這是imho最短的方式;如果你需要高精度的話,你將不得不做3個嵌套switch語句。 – dst