Finite State Machine

Finite State Machines

Even Binary Numbers

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public class EvenBinary{ public static void main(String[] args) { String [] ls = {"10", "111", "01"}; for (String s : ls) System.out.printf("%10s, %s\n", s,sm(s)); } public enum States {START,FAIL,A,B}; public static boolean sm(String s) { States state = States.START; int i=0; while (i<s.length() && state!=States.FAIL) { char c = s.charAt(i); switch (state){ case START: if (c=='1') state = States.B; else state = States.FAIL; break; case A: if (c=='0') state = States.A; else if (c=='1') state = States.B; else state = States.FAIL; break; case B: if (c=='0') state = States.A; else if (c=='1') state = States.B; else state = States.FAIL; break; } i++; } return state==States.A; } }

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test text

 

 

 

 

Even Binary Numbers - Abstracted

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import java.util.HashMap; public class EvenBinary{ public static void main(String[] args) { String [] ls = {"10", "111", "01"}; for (String s : ls) System.out.printf("%10s, %s\n", s,sm(s)); } public enum States {S,A,B}; public static boolean sm(String s) { HashMap<States,HashMap<String,States>> d = new HashMap<States,HashMap<String,States>>(); d.put(States.S,new HashMap<String,States>()); d.put(States.A,new HashMap<String,States>()); d.put(States.B,new HashMap<String,States>()); d.get(States.S).put("1",States.B); d.get(States.A).put("0",States.A); d.get(States.A).put("1",States.B); d.get(States.B).put("0",States.A); d.get(States.B).put("1",States.B); States state = States.S; int i=0; while (i<s.length() && state!=null) { String c = s.substring(i,i+1); state = d.get(state).get(c); i++; } return state==States.A; } }

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test text

 

 

 

 

Divisible by Three (decimal)

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public class Div3 { public static void main(String[] args) { String [] ls = {"10", "111", "01","123"}; for (String s : ls) System.out.printf("%10s, %s\n", s,sm(s)); } public enum States {FAIL,A,B,C}; public static boolean sm(String s) { States state = States.A; int i=0; while (i<s.length() && state!=States.FAIL) { char c = s.charAt(i); switch (state){ case A: if (c=='0' || c=='3' || c=='6' || c=='9') state = States.A; else if (c=='1'||c=='4'||c=='7') state = States.B; else if (c=='2'||c=='5'||c=='8') state = States.C; break; case B: if (c=='0' || c=='3' || c=='6' || c=='9') state = States.B; else if (c=='1'||c=='4'||c=='7') state = States.C; else if (c=='2'||c=='5'||c=='8') state = States.A; break; case C: if (c=='0' || c=='3' || c=='6' || c=='9') state = States.C; else if (c=='1'||c=='4'||c=='7') state = States.A; else if (c=='2'||c=='5'||c=='8') state = States.B; break; } i++; } return state==States.A; } }

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test text