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Flow of Control

Flow of Control. Flow of Control. The Flow of control is the order in which a program performs actions . Up to this point, the order has been sequential . A branching statement chooses between two or more possible actions .

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Flow of Control

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  1. Flow of Control

  2. Flow of Control • The Flow of control is the order in which a program performs actions. • Up to this point, the order has been sequential. • Abranching statementchooses between two or more possible actions. • Note that a loop statement repeats an action until a stopping condition occurs.

  3. if-else statement (Cont.) • It is a branching statement that chooses between two possible actions. • Syntax: if (Boolean_Expression) Statement_1 else Statement_2 • Example:

  4. if-else statement (Cont.)

  5. More one if-else • To include multiple statements in a branch, enclose the statements in braces. if (count < 3) { total = 0; count = 0; } • Omitting else: • The value of a booleanexpression is either true or false, for instance, count < 3.

  6. Java Comparison Operators

  7. Compound Boolean Exp. • Boolean expressions can be combined using “and”, i.e., &&. (sub_expression_1) && (sub_expression_2) • if ((score > 0) && (score <= 100))not allowed if (0 < score <= 100) • The larger expression is true only when both of the smaller expressions are true. • Boolean expressions can be combined using the “or”, i.e., ||. (sub_expression_1) || (sub_expression_2) • if ((quantity > 5) || (cost < 10)) • The larger expression is true when either of the smaller expressions is true or bothof the smaller expressions are true.

  8. Negating a Boolean Exp. • A boolean expression can be negated using the "not”, i.e., !. !(boolean_expression) • (a || b) && !(a && b) • which is the exclusive or • Avoiding the negation operator:

  9. Java Logical Operators

  10. Using Equality • Appropriatefor determining if two integers or characters have the same value. • if (a == 3)where a is an integer type. • Not appropriate for determining if two floating points values are equal. Use < and some appropriate tolerance. • if (abs(b - c) < epsilon)where b, c, epsilonare floating point types. • Not suitablefor defining if 2 objects have the same value. • if (s1 == s2), where s1 and s2 refer to strings, determines only if s1 and s2 refer the a common memory location. • (s1 == s2) is false, if s1 and s2 refer to strings with identical sequences of characters, but stored in different memory locations.

  11. Equality For Objects • To test the equality for objects of String, use method equals. s1.equals(s2) or s2.equals(s1) • To test for equality ignoring case, use equalsIgnoreCase. ("Hello".equalsIgnoreCase("hello")) • Syntax: String.equals(Other_String) String.equalsIgnoreCase(Other_String)

  12. Lexicographic Order • The lexicographic order is similar to alphabetical order, but is it based on the order of the characters in the ASCII table, a.k.aunicode, (see page 932). • All the digits come before all the letters. • The uppercase letters come before the lowercase letters. • Strings consisting of alphabetical characters can be compared using method compareTo and method toUpperCase or method toLowerCase.

  13. Lexicographic Order (Cont.) • Example. String s1 = "Hello"; String lowerS1 = s1.toLowerCase(); String s2 = "hello"; if (lowerS1.compareTo(s2) == 0) System.out.println("Equal!"); • Syntax: String_1.compareTo(String_2) • MethodcompareToreturns • a negative number if String_1 precedes String_2 • zero if the two strings are equal • a positive number of String_2 precedes String_1.

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