Chapter+3+String+Compare

Comparing Strings and Generating Random Numbers

Chapter Overview

Chapter 3 focuses on comparing strings and generating random numbers in programming.

User Input and Conditional Statements

Age Input Example

Code Example:

Scanner in = new Scanner(System.in);
System.out.print("enter your age: ");
int age = in.nextInt();
in.nextLine();
if(age == 16)  
    System.out.println("your first year eligible to drive");
else  
    System.out.println("not your first year of eligibility");

Name Input Example

Code Example:

Scanner in = new Scanner(System.in);
System.out.print("enter your name: ");
String name = in.nextLine();
if(name == "Mr. Ellis") {
    System.out.print("you are the teacher");
} else {
    System.out.print("you are a student");
}

String Comparison

Comparing Strings

Strings should not be compared using ==, as it checks for reference equality.
Use the .equals() method to compare string values:

String name = "Mr. Ellis";
if(name.equals("Mr. Ellis"))
    System.out.print("this works");

Case Sensitivity

String comparison using .equals() is case-sensitive:

String str = "Mr. Ellis";
if (str.equals("Mr. Ellis"))  // prints "yes"
if (str.equals("mr. ellis")) // does not print "yes"

Correct String Comparison

Always use .equals() for string comparisons:

Scanner in = new Scanner(System.in);
String name = in.nextLine();
if(name.equals("Mr. Ellis")) {
    System.out.print("you are the teacher");
} else {
    System.out.print("you are a student");
}

Ignoring Case in Comparisons

To ignore case, use .toLowerCase() or .toUpperCase():

String str = "Mr. Ellis";
if (str.toLowerCase().equals("mr. ellis"))
    System.out.print("yes");  // prints "yes"

Generating Random Numbers

Random Class Overview

Import statement must be included:

import java.util.Random;

Create an instance of the Random class to generate random numbers:

Random rand = new Random();

Use the nextInt(max) method to generate a random number from 0 to max (exclusive):

int myRand = rand.nextInt(10); // random number from 0-10

Random Number Example

Code Example:

Random myRand = new Random();
int randNum = myRand.nextInt(10);
System.out.print("random number: " + randNum);
if(randNum == 1)
    System.out.print("you’re number one!");