Object creating statement in Java doesn't allow to use a single-line loop. Why?

Question

The following program has no importance of its own. It just counts the number of objects created through the use of a for loop using a static field inside the class Counter

Answer 1

To understand why this happens, you have to look at Java's Blocks and Statements syntax in the language specification.

A ForStatement is defined as:

ForStatement:
    for ( ForInitopt ; Expressionopt ; ForUpdateopt )
        Statement

Statement is defined as:

Statement:
    StatementWithoutTrailingSubstatement
    LabeledStatement
    IfThenStatement
    IfThenElseStatement
    WhileStatement
    ForStatement

StatementWithoutTrailingSubstatement:
    Block
    EmptyStatement
    ExpressionStatement
    SwitchStatement
    DoStatement
    BreakStatement
    ContinueStatement
    ReturnStatement
    SynchronizedStatement
    ThrowStatement
    TryStatement

Then, looking at Block:

Block:
    { BlockStatementsopt }

BlockStatements:
    BlockStatement
    BlockStatements BlockStatement

BlockStatement:
    LocalVariableDeclarationStatement
    ClassDeclaration
    Statement

You'll notice that, within this specification, LocalVariableDeclarationStatement is not valid unless it is in a block. But, because the ForStatement requires that it is followed by a statement, there MUST exist parenthesis in order to make the expression valid. As such, any local variable declaration would be invalid in the loop without the brackets.