Hands On Java Lab 3 Exercise Lab 3: Java Expressions Introduction Today's exercise involves a series of experiments, each investigating a different aspect of a fundamental Java concept: the expression. The term expression can be defined as follows: An expression is a sequence of one or more operands, and zero or more operators, that when combined, produce a value. To illustrate, the sequence
12
fits the definition of an expression, since it consists of one operand (12) and zero operators that combine to produce a value (12). Perhaps more familiarly, the sequence
2 + 3
fits the definition of an expression, since it consists of two operands (2 and 3) and one operator (+) that combine to produce a value (5). Operands need not be constants: the sequence
2.5 * x - 1.0
fits the definition of an expression, since it consists of three operands (2.5, x and 1.0) and two operators (*, -) that combine to produce a value (1 less than the product of 2.5 and x). These last two examples have been arithmetic expressions, that is, expressions whose operators are familiar arithmetic operators. As we shall see in today's exercise, Java provides a rich set of both arithmetic and non-arithmetic operators that allow Java programmers to construct expressions. The Experimental Laboratory Using what you have learned previously, begin by creating an Express project as appropriate for your environment. We will use the file Express.java as a software laboratory for most of the experiments in this exercise. Click on the preceding link, and use your browser's
File -> Save As
menu choice to save this file in your Express project directory. Add Express.java to your project if needed. You can then open the file and take a moment to study its contents. In our print() and println() statements, we have expressions of the form Expression1 + Expression2 + ... + ExpressionN;
where some of the expressions are characters or strings. The exact details are fairly complicated, but the net effect is that Expression1 is evaluated and displayed, after which Expression2 is evaluated and displayed, after which ..., after which ExpressionN is evaluated and displayed. An output statement thus provides a simple "laboratory" in which we can "experiment" with expressions by building them and viewing the values they produce. Note that the parentheses around the i + j are required if we actually want to print the sum of i and j and not the value of i followed by the value of j. Experiments Below is a list of the experiments available for this exercise. Your instructor will tell you which ones you can omit, if any. For each experiment that you are to perform, click its link and print a hard copy of the resulting web page. Then record your experimental results on that hard copy. Experiment 1: Simple Expressions Experiment 2: Characters and Character Strings Experiment 3: Arithmetic Expressions Experiment 4: Relational Expressions Experiment 5: Logical Expressions Experiment 6: Operator Precedence Experiment 7: Operator Associativity Experiment 8: Expressions Containing Functions Experiment 9: Declarations Experiment 10: Constant Declarations Experiment 11: Assignment Statements Experiment 12: Assignment Associativity Experiment 13: Assignment Shortcuts Experiment 14: Increment and Decrement Expressions Phrases you should now understand: Expression, Simple Expression, Operand, Operator, Operator Precedence, Operator Associativity, Integer Division, Logical Operator, Boolean Operator, Libraries of Methods, Variable Declaration, Constant Declaration, Operator Chaining, Increment Expression, Decrement Expression. Submit: Turn in to your instructor the hard copies showing the results of each of your experiments, plus a hard copy of your final version of Express.java. Back to the Prelab Questions Back to This Lab's Table of Contents Forward to the Homework Projects Back to the Table of Contents Back to the Introduction Copyright 2000 by Prentice Hall. All rights reserved.
