When is an unassigned expression a valid statement?

Question

I\'ve read Oracle\'s expressions tutorial and couldn\'t understand this.

It is well known that the following line of code is valid Java syntax:

new O         


        

Answer 1

The rule is in the Java Language Specification:

Certain kinds of expressions may be used as statements by following them with semicolons.

ExpressionStatement:

• StatementExpression ;

StatementExpression:

• Assignment
• PreIncrementExpression
• PreDecrementExpression
• PostIncrementExpression
• PostDecrementExpression
• MethodInvocation
• ClassInstanceCreationExpression

You see that a constructor invocation is a statement. But a String literal or mathematical expression is not.