2020-01-15 23:07:02 -05:00
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2022-02-15 01:14:58 -05:00
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2020-01-15 23:07:02 -05:00
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< h1 > Lecture in CPSC 220 Sept 25 2017< / h1 >
< h2 > Constants< / h2 >
< p > Adding the keyword < code > final< / code > in front of a variable declaration makes the variable constant. Meaning you cannot later change it in the code.< / p >
< pre > < code class = "language-java" > final int MAX = 10;< / code > < / pre >
< p > By industry norm, the style of the variable is to have it in all caps.< / p >
< p > You CANNOT do the following< / p >
< pre > < code class = "language-java" > final int MAX = 10;
MAX = 15;< / code > < / pre >
< h2 > Using Libraries< / h2 >
< ol >
< li > Import the library< / li >
< li > Find the method that is appropriate< / li >
< li > Use it< / li >
< / ol >
< p > Example:< / p >
< pre > < code class = "language-java" > import java.util.Math;
public class MathTest {
public static void main(String[] args) {
double answer = Math.ceil(5.4);
System.out.println(Math.ceil(4.5));
}
}< / code > < / pre >
< h2 > Typecasting / Type Conversions< / h2 >
< p > You can only cast a variable if you are casting it to a type that is larger than the one it was previously. The expression Polack used is that you cannot fit into super skinny jeans, but you can fit into bigger pants.< / p >
< pre > < code class = "language-java" > double dnum;
float fnum;
int inum;
dnum = (double)fnum * (double)inum;< / code > < / pre >
< h2 > Char vs String< / h2 >
< p > < code > String< / code > s are initialized in Java with double quotes while < code > char< / code > s are initialized with single quotes< / p >
< pre > < code class = "language-java" > char initial = 'j';
String name = "Jennifer";< / code > < / pre >
< p > Characters can be read in as an integer.< / p >
< h2 > Random Numbers< / h2 >
< ol >
< li > Import < code > java.util.Random;< / code > < / li >
< li > Declare the random number generator< / li >
< li > Initialize with < code > new< / code > < / li >
< li > Use it< / li >
< / ol >
< pre > < code class = "language-java" > import java.util.Random;
public class RandTest {
public static void main(String[] args) {
Random rand;
rand = new Random();
int number = rand.nextInt(100); // Random generates number between 0-99
}
}< / code > < / pre >
< p > How do you generate numbers in a different range? [50, 150]< / p >
< pre > < code class = "language-java" > rand.nextInt(100); // 0-99
rand.nextInt(101) // 0 - 100
rand.nextInt(101) + 50 //50-150< / code > < / pre >
< p > In more general terms< / p >
< pre > < code class = "language-java" > rand.nextInt(end - start + 1) + start< / code > < / pre >
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