Blocks

BASIC

A block is some number (possibly zero) of declarations and statements, enclosed in braces. A block is itself considered to be a statement.

The body of a method is always a block. However, the braces enclosing the contents of a class or interface are not considered to be a block, and the scope rules and access rules are different. For example:

public class HelloWorld { // not a block
    String name = "World";
    public static void main(String[] args) { // a block
        System.out.println("Hello, " + name);
    }
}

Control statements, such as if statements and loops, control the execution of a single statement. If you want to control more than just one statement, you can enclose those statements in curly braces to make them into a block (which counts as a single statement). For example:

if (x < y) {
    int temp = x;
    x = y;
    y = temp;
}

If x is less than y, the above code interchanges the values of x and y (using a temporary variable); otherwise, it does nothing.

If your block contains declarations (such as int temp = x;), you should normally put them first, before the statements in the block. Any variable you declare inside a block can be used from where you declare it up to the end of the block--this is the "scope" of the variable.

A block is the only kind of statement that does not end in a semicolon. Statements within the block, however, do end in semicolons (as usual).

INTERMEDIATE

Declarations in a block may shadow other declarations.