CS125: Introduction to Programming Principles

What You Should Know

The last two lectures introduced Boards, Strings and Scanners. Here is a quick run down of what you should know for this lab. You are also expected to understand everything from the previous labs. Please feel free to go back to previous lab and redo parts you had difficultlies with.

• You need to make your own programs from scratch. If you've forgotten, this is what you need to do to make a program called "Example.java".

  
  		public class Example
  		{
  		   public static void main( String[] args )
  		   {
  		      // Your code here!
  		   }
  		}
  		
  

  Remember to change the name of the class to match the name of the file you are creating.

• Scanner Class: How we get input into our program. Some methods include .nextLine() and .close. Refer to documentation for more Scanner methods.

• String Class: This class is used for storing sentences. A char, which is a primitive type, only stores single characters. A string can store multiple characters. To use it you would type:

  		String aString = "My Message";
  	

• Once you have a string, like any other object we have looked at, you can perform operations on it such as .charAt(int position), .indexOf(char c), .indexOf(String s), and .substring(int start).
  An example of using one would be:

  	
  		char a = aString.charAt(1);
  		
  		System.out.println(a);	// outputs 'y' since 'y' is in the first position 
  		
  		//NOTE: Recall that counting starts at 0 (i.e. 'M' is at the 0th position, 'y' is the 1st, etc.)
  		
  	

• The "+" operator works differently than numeric addition when one of the two operands is a String. If one operand is a String type, then the other operand is converted to a String (if it is not already) and then performs String concatenation.
  For example:

  	
  		int x = 5;
  		
  		String s1 = "hello";		
  		
  		String s2 = x + s1;
  		
  		System.out.println(s2);  // outputs the string "5hello"
  		
  	

• For a list of all String methods see documentation. (Found on this site under Resources --> Java Resources --> Selected String Methods)

  If you do not understand a point above, please consult a tutor, TA or instructor immediately as this will become a critical part of the course.