#regularexpressionexamplesinjava

Regular Expression Examples

  Describe The Following Sets Of Regular Expressions {0,1,2}  {∧,ab} {abb,a,b} {∧,0,00,000....} {1,11,111,1111,......} How To Form Regular Expressions From Above Sets??  

1.{0,1,2}

This Is The Set Given Containing Symbols 0,1,2 That Means It Could Contain 0 Or 1 Or 2 These Are Symbols Contained In The Set.   In Regular Expression, It Can Be Written Like This R=0+1+2 // + Is Or  

2.{∧,ab}  // ∧ Is Empty Symbol

The Above Set Will Be Denoted Like This R=∧ ab // If You See The First Set {0,1,2}, In This Set The Empty Symbol Was Not Included And This Contains More Than One Symbol, We Used The '+' Symbol To Denote. But In This Set {∧, ab}, There Only One Symbol(ab) And An Empty Symbol Empty(∧) Symbol Along With It, You Don't Have To Use The '+' Or "or" Symbol You Can Just Write ∧ And ab R=∧ ab // This Is The Regular Expression.  

3) {abb,a,b,bba}

The Given Set Contains abb a b bba So, This Means That It Can Be Anything Like abb Or a Or b Or bba So Any Of These Symbols Can Be Present In The Set. Or A Language That Which Contains These Any Of These Symbols Will Be Accepted. Regular Expression For The Given Set Is  R=abb+a+b+bba // + Means Or  

4) {∧,0,00,000....}

If You Look The Given Set Carefully, You Find That These Are Any Strings That Can Be Formed By Using The '0' Symbol 0 00 000 0000....Any More 0's That Can Be Formed By Putting Together Any Number Of 0's That You Want So All The Strings That Can Be Formed Using  0 Along With The Symbol ∧ Empty Symbol, It Denotes The Closure Of 0   So {∧,0,00,000....} This Is The Closure Of 0 So How Do We Denote Regular Expression Closure R=0* // * Denotes The Closure  

5) {1,11,111,1111,......}