Driver program to test above function
public static void main ( String [ ] args ) { String expr1 = "1 + 2*5 + 3" ; int res = evaluate ( expr1 ) ; if ( res == - 1 ) System . out . println ( expr1 + " ▁ is ▁ Invalid " ) ; elseSystem . out . println ( " Value ▁ of ▁ " + expr1 + " ▁ is ▁ " + res ) ; String expr2 = "1 + 2*3" ; res = evaluate ( expr2 ) ; if ( res == - 1 ) System . out . println ( expr2 + " ▁ is ▁ Invalid " ) ; elseSystem . out . println ( " Value ▁ of ▁ " + expr2 + " ▁ is ▁ " + res ) ; String expr3 = "4-2 + 6*3" ; res = evaluate ( expr3 ) ; if ( res == - 1 ) System . out . println ( expr3 + " ▁ is ▁ Invalid " ) ; elseSystem . out . println ( " Value ▁ of ▁ " + expr3 + " ▁ is ▁ " + res ) ; String expr4 = "1 + + 2" ; res = evaluate ( expr4 ) ; if ( res == - 1 ) System . out . println ( expr4 + " ▁ is ▁ Invalid " ) ; elseSystem . out . println ( " Value ▁ of ▁ " + expr4 + " ▁ is ▁ " + res ) ; } }