Flow Control and Exception Handling - if...else Statement

Syntax

    if( boolean expression ) {
        statement1;
        ...
        statementn;
    }    
        
    if( boolean expression ) {
        statement1;
        ....
        statementn;
    } else {
        statementa;
        ...
        statementz;
    }    

• the expression must be a boolean type
• curly braces are only required if there is more than one execution statement
• in the first form, the statements are only executed if the boolean expression evaluates to true
• in the second form, the first set of statements are executed if the boolean expression evaluates to true; otherwise, the statements following else are executed
• may be nested

    if( x == y ) {
      // do this
    } else if( x > y ) {        // nested 'if'
      // do this
    } else {
      // do this
    }    

Example Code

• TestIf.java

Traps

• a non-boolean value used in the if( )
• using the assignment operator '=' vs '=='