public <E> void setExpression(Expression<E> expression) {
        Preconditions.checkState(this.expression == null, "An expression is already set");
        this.expression = expression;
    }
public <E> void setExpression(Expression<E> expression) {
        Preconditions.checkState(this.expression == null, "An expression is already set");
        this.expression = expression;
    }
public < E > void setExpression ( Expression < E > expression ) { Preconditions . checkState ( this . expression == null , "An expression is already set" ) ; this . expression = expression ; }
Sets the expression currently active in the building context.

@param expression the expression.
@param <E>        the type of the expressions.
Sets the expression currently active in the building context .