 |  |  |  |
| | | |
if, else, and elif become if, else, and else if, respectively. The most basic of these is if. Let's write some code to test the parity of an integer: (The percent sign is the modulus operator, just as in Python.)
public static void main(String[] args) {
System.out.println("Hello, World!");
int x = 5;
if (x % 2 == 0) {
System.out.println("x is even.");
} else {
System.out.println("x is odd.");
}
}
Try running this, then change x to an even number and run it again. Notice that squiggly braces are used to delimit the different branches of the conditional, instead of relying on indentation levels. Notice also that the condition must be in parentheses, unlike Python. If you don't include those parentheses, you'll get some syntax errors:
$ javac *.java
CodeToRun.java:7: error: '(' expected
if x % 2 == 0 {
^
CodeToRun.java:7: error: ')' expected
if x % 2 == 0 {
^
2 errors
Let's do another conditional, except that we'll test the sign of the integer:
public static void main(String[] args) {
System.out.println("Hello, World!");
int x = 5;
if (x < 0) {
System.out.println("x is negative.");
} else {
System.out.println("x is positive.");
}
}
If you try running this with different values, you might notice that you'll be lied to! Especially if you set x to zero. (Zero is neither positive nor negative.) Let's change the conditional to reflect this change by chaining the branches:
public static void main(String[] args) {
System.out.println("Hello, World!");
int x = 5;
if (x < 0) {
System.out.println("x is negative.");
} else if (x > 0) {
System.out.println("x is positive.");
} else {
System.out.println("x is zero.");
}
}
Java does not bother to shorten else if into elif. Other than that, the functionality of chained conditionals works the same. We can have as many branches as we want, and it's not necessary to have a final else branch.
Rewrite your Monkey class so that it only prints one sentence, but still describes whether the monkey is funny or not without using the words 'true' and 'false'. Mine does this (when the boolean variable is true):
$ javac *.java $ java Monkey Dominoa is a funny monkey with 4 teeth and a 26.34-inch long tail.
Here's what it does when the boolean variable is false:
$ javac *.java $ java Monkey Dominoa is not a funny monkey with 4 teeth and a 26.34-inch long tail.
You'll need to use multiple print statements to make it work. Don't forget to test both ways!