How to reduce if statements [closed]

Question

The program below functions as necessary but how do I reduce the amount of if statements. I have been told that if your function contains 2 or more if statements then your doing it wrong. Any suggestions? I've tried using switch statements but that hasn't worked because the case can't be a boolean.

for(int i = 1; i < 100; i++)         {         if(i % 10 == 3)          {             System.out.println("Fizz" + "(" + i + ") 3%10");         }          if(i / 10 == 3)         {             System.out.println("Fizz" + "(" + i + ") 3/10");         }           if(i % 10 == 5)          {             System.out.println("Buzz" + "(" + i + ") 5%10");         }          if(i / 10 == 5)         {             System.out.println("Fizz" + "(" + i + ") 5/10");         }          if(i / 10 == 7)         {             System.out.println("Fizz" + "(" + i + ") 7/10");         }          if(i%10 == 7)         {             System.out.println("Woof" + "(" + i + ") 7%10");         }          if(i % 3 == 0)         {             System.out.println("Fizz" + "(" + i + ") 3%==0");         }          if(i % 5 == 0)         {             System.out.println("Buzz" + "(" + i + ")5%==0");         }          if(i % 7 == 0)         {             System.out.println("Woof" + "(" + i + ")7%==0");             }          if( (i % 7 !=0 ) && (i % 3 !=0 ) && (i % 5 !=0 )                 && (i % 10 !=3) && (i % 10 !=5 ) && (i%10 !=7 ) )             System.out.println(i);     } 

Answer 1

How about creating a method for the cases:

 public void printIfMod(int value, int mod){        if (value % 10 == mod)           System.out.println(...);  }   public void printIfDiv(int value, int div){        if (value / 10 == div)           System.out.println(...);  } 

Then instead of a bunch of if you have a set of calls the the two methods. You might even create a single method that calls both of the above.

 public void printIf(int value, int div){       printIfMod(value, div);       printIfDiv(value, div);  }   for(int i = 1; i < 100; i++) {       printIf(i, 3);       printIf(i, 5);       ....  } 

In the above code the number of ifs is less of an issue to me than the amount of repeated code.

Answer 2

Here's a slight improvement using two switch statements

switch(i / 10){   case 3: // do something     break;   case 5: // do something else     break;   case 7: // do something else     break; }  switch(i % 10){   case 3: // do something     break;   case 5: // do something else     break;   case 7: // do something else     break; } 

Unfortunately you'll need one switch statement per divisor.

Alternatively, you can embrace OOP and come up with an abstraction like this:

public abstract class Processor {     private final int divisor;     private final int result;     private final boolean useDiv; // if true, use /, else use %      public Processor(int divisor, int result, boolean useDiv) {         this.divisor = divisor;         this.result = result;         this.useDiv = useDiv;     }     public final void process(int i){         if (              (useDiv && i / divisor == result)              || (!useDiv && i % divisor == result)            ){                 doProcess(i);             }     }      protected abstract void doProcess(int i); } 

Sample usage:

public static void main(String[] args) {     List<Processor> processors = new ArrayList<>();     processors.add(new Processor(10, 3, false) {         @Override         protected void doProcess(int i) {             System.out.println("Fizz" + "(" + i + ") 3%10");         }     });     // add more processors here     for(int i = 1; i < 100; i++){         for (Processor processor : processors) {             processor.process(i);         }     }  }