Unit 3
Discussing what I learned from code.org this week.
- What is an if statement?
- What is an if/else statement?
- What is an If-else If-else Statement?
- 5 If-Else Statements
- What is a Switch Case Program in Java?
- De Morgan's Law
- Random Math Class
- Compound Boolean Expressions
- Truth Table
- Comparing Numbers
- Comparing Strings
- Comparing Objects
if (5 > 2) { //the program decides whether this is true or not
System.out.println("5 is greater than 2"); //if it is then this line is printed
}
The if/else statement executes a block of code if a specified condition is true. If the condition is false, another block of code can be executed.
int time = 20; //set variable
if (time < 18) { //the program decides whether this is true or not
System.out.println("Good day."); //if it is then print this line
} else {
System.out.println("Good evening."); //if it is not then print this
}
int time = 22;
if (time < 10) { //the program decides whether this is true or not
System.out.println("Good morning."); //if it is then print this line
} else if (time < 20) { //if it is not true, then check if this is true
System.out.println("Good day."); //if it is then print this line
} else {
System.out.println("Good evening."); //or else print this line
}
Each
if (5 > 3) {
System.out.println("5 is greater than 3");
}
else if(5 < 3) {
System.out.println("5 is less than 3");
}
else if (6 > 7) {
System.out.println("6 is greater than 7");
}
else if (10 < 7) {
System.out.println("10 is less than 7");
}
else {
System.out.println("Invalid");
}
The switch statement is a multi-way branch statement. In simple words, the Java switch statement executes one statement from multiple conditions.
int x = 1; // the integer given in the variable is 20
String output;
switch (x) {
case 1:
output = x + " > 0";
break;
case 2:
output = x + " > 2";
break;
case 3:
output = x + " > 3";
break;
case 4:
output = x + " > 4";
break;
}
System.out.println(output)
The complement of the union of two sets is the intersection of their complements and the complement of the intersection of two sets is the union of their complements.
|| means "or" and the && means "and"
boolean blue = true;
boolean red = true;
if (!(blue && red)){
System.out.println("I do not like blue or red");
}
else{
System.out.println("My favorite colors are blue and red");
}
if (!blue || !red){
System.out.println("I do not like red or blue");
}
else{
System.out.println("My favorite colors are red and blue");
}
The random math class allows you to generate random numbers throughout your code. You can specify certain ranges where you would like the number to be in.
// Java program to demonstrate working
// of java.lang.Math.random() method
import java.lang.Math;
class Gfg1 {
// driver code
public static void main(String args[])
{
// Generate random number
double rand = Math.random();
// Output is different everytime this code is executed
System.out.println("Random Number:" + rand);
}
}
If two boolean values/expressions are combined with a logical and (&&) and the first expression is false, then the second expression won't be executed.
public class Test2
{
public static void main(String[] args)
{
boolean walking = false;
boolean carIsAvailable = false;
if (walking || carIsAvailable)
{
System.out.println("You can go out");
}
else
{
System.out.println("No, you can't go out");
}
}
}
shows how the truth or falsity of a compound statement depends on the truth or falsity of the simple statements from which it's constructed
first case printed when x = 3 and y = 9
if (x > 0 && (y / x) == 3)
{
System.out.println("first case");
}
else
{
System.out.println("second case");
}
To check two numbers for equality in Java, we can use the Equals() method as well as the == operator.
Integer val1 = new Integer(5);
Integer val2 = new Integer(5);
(val1 == val2)
public class Demo {
public static void main( String args[] ) {
Integer val1 = new Integer(5);
Integer val2 = new Integer(5);
Integer val3 = new Integer(10);
System.out.println("Integer 1 = "+val1);
System.out.println("Integer 2 = "+val2);
System.out.println("Integer 3 = "+val3);
System.out.println("val1 is equal to val2 = "+(val1 == val2));
System.out.println("val2 is not equal to val3 = "+(val2 != val3));
}
}
// Java program to Compare two strings
// lexicographically
public class GFG {
public static void main(String args[])
{
String string1 = new String("Geeksforgeeks");
String string2 = new String("Practice");
String string3 = new String("Geeks");
String string4 = new String("Geeks");
String string5 = new String("geeks");
// Comparing for String 1 != String 2
System.out.println("Comparing " + string1 + " and " + string2
+ " : " + string1.equalsIgnoreCase(string2));
// Comparing for String 3 = String 4
System.out.println("Comparing " + string3 + " and " + string4
+ " : " + string3.equalsIgnoreCase(string4));
// Comparing for String 4 = String 5
System.out.println("Comparing " + string4 + " and " + string5
+ " : " + string4.equalsIgnoreCase(string5));
// Comparing for String 1 != String 4
System.out.println("Comparing " + string1 + " and " + string4
+ " : " + string1.equalsIgnoreCase(string4));
}
}
assertThat(1 == 1).isTrue();
Integer a = new Integer(1);
assertThat(1 == a).isTrue();