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Ternary Operator (If-Then-Else)
You can use the ternary operator for performing if-then-else conditional logic inside the expression. The following listing shows a minimal example:
-
Java
-
Kotlin
String falseString = parser.parseExpression(
"false ? 'trueExp' : 'falseExp'").getValue(String.class);
val falseString = parser.parseExpression(
"false ? 'trueExp' : 'falseExp'").getValue(String::class.java)
In this case, the boolean false
results in returning the string value 'falseExp'
. A more
realistic example follows:
-
Java
-
Kotlin
parser.parseExpression("name").setValue(societyContext, "IEEE");
societyContext.setVariable("queryName", "Nikola Tesla");
expression = "isMember(#queryName)? #queryName + ' is a member of the ' " +
"+ Name + ' Society' : #queryName + ' is not a member of the ' + Name + ' Society'";
String queryResultString = parser.parseExpression(expression)
.getValue(societyContext, String.class);
// queryResultString = "Nikola Tesla is a member of the IEEE Society"
parser.parseExpression("name").setValue(societyContext, "IEEE")
societyContext.setVariable("queryName", "Nikola Tesla")
expression = "isMember(#queryName)? #queryName + ' is a member of the ' " + "+ Name + ' Society' : #queryName + ' is not a member of the ' + Name + ' Society'"
val queryResultString = parser.parseExpression(expression)
.getValue(societyContext, String::class.java)
// queryResultString = "Nikola Tesla is a member of the IEEE Society"
See the next section on the Elvis operator for an even shorter syntax for the ternary operator.