Decision Making
Read this chapter, which reviews how computers make decisions using if statements. As you read this tutorial, you will understand that sometimes it is important to evaluate the value of an expression and perform a task if the value comes out to be true and another task if it is false. In particular, try the simulated program under the heading "Simulated Program" to see how a different response is presented to the user based on if a number is positive or negative.
Pay special attention to the "More Than One Statement per Branch" header to learn how the 'else' statement is used when there is more than one choice.
4. Checking a String
Answer:
If the user enters anything other than exactly the single character Y then the "false branch" is executed.
Checking a String
The if statement
if ( answer.equals("Y") ) picks either the "true branch" or the "false branch" . Only one branch or the other is executed, just as in the flow chart. This part of the statement
answer.equals("Y") evaluates to true if the string referenced by answer contains exactly the single character "Y" . For anything else it evaluates to false. This is somewhat awkward. Dealing with user input is often awkward. Later on you will see better ways to do this. Here are some runs of the program:
C:\Examples>javac RainTester.java
C:\Examples>java RainTester
Is it raining? (Y or N): Y
Wipers On
C:\Examples>java RainTester
Is it raining? (Y or N): N
Wipers Off
C:\Examples>java RainTester
Is it raining? (Y or N): Yes
Wipers Off
C:\Examples>java RainTester
Is it raining? (Y or N): Rats
Wipers Off
Question 4:
Is the integer -12 negative or not?