Hello, I was creating a program to learn c++. I did switch elements 1 and 2 perfectly. I could not get the case 3 to work at all. Please help me.
import javax.swing.*;
 
import java.awt.*;
 
public class learningByChapter extends java.applet.Applet {
 
 
	String statement = "a single set of commands";
	String comment = "a line or portion of a line that is ignored by the C++ compiler";
	String declaration = " a statement that defines a variable";
	String variable = " a holding place in the computer's memory" +
			" to store a value of some type";
	String expression = " a command that has a value";
	String operator = " a command that generates a value";
 
	String vocabulary = "a statement is " + statement + "\na comment is " + comment + 
	"\na declaration is " + declaration + "\na variable is " + variable + "\nan expression is " + 
	expression + "an operator is " + operator;
	TextArea letter;
 
 
	public void init(){
 
		String chapters = JOptionPane.showInputDialog("chapter1\n" + "chapter2\n"
				+ "chapter3\n" + "chapter4\n");
		int choice = Integer.parseInt(chapters);
		switch(choice){
		case 1:		
		String statement = "a single set of commands";
		String comment = "a line or portion of a line that is ignored by the C++ compiler";
		String declaration = " a statement that defines a variable";
		String variable = " a holding place in the computer's memory" +
				" to store a value of some type";
		String expression = " a command that has a value";
		String operator = " a command that generates a value";
		//TextArea
 
		//TextArea
 
		String letter = "Learn this mom. I made this for you! Study well because a test will follow. " + "\n\n\na statement is " + 
		statement + "\na comment is " + comment + "\na declaration is " + declaration +
		"\na variable is " + variable + "\nan expression is " + expression + "\nan operator is " + operator + "\n\n\nan " +
				"expression example is int x = 3;" + "\na declaration example is JTextArea outputArea; " + "\na comment example is // initializing" +
				"\na variable example is output" + "\nanother variable example is x " + "\na statement example is System.out.println();" +
				"\nan operator example is = " + "\nanother operator example is - " + "\nanother operator example is + ";
		;
		TextArea let;
	let = new TextArea(letter,40,90);
	add(let);
	JOptionPane.showMessageDialog(null,let);
		//Quiz
		JOptionPane.showMessageDialog(null,"what is a statement");
		String answer = JOptionPane.showInputDialog("A - " + statement + "\n" +
				"B - " + comment + "\n" + "C - "  + 
				declaration + "\n" + "D - " + variable + "\n" + "E - " + expression
				 + "\n" + "F - " + operator);
		if(answer.equals("A"))
			JOptionPane.showMessageDialog(null,"correct");
		else
			JOptionPane.showMessageDialog(null,"incorrect");
 
		//introducing the new question
 
		JOptionPane.showMessageDialog(null,"what is a comment");
		String answer2 = JOptionPane.showInputDialog("A - " + statement + "\n" +
				"B - " + comment + "\n" + "C - "  + 
				declaration + "\n" + "D - " + variable + "\n" + "E - " + expression
				 + "\n" + "F - " + operator);
		if(answer2.equals("B"))
			JOptionPane.showMessageDialog(null,"correct");
		else
			JOptionPane.showMessageDialog(null,"incorrect");
 
		//introducing the new question
 
		JOptionPane.showMessageDialog(null,"what is a variable");
		String answer3 = JOptionPane.showInputDialog("A - " + statement + "\n" +
				"B - " + comment + "\n" + "C - "  + 
				declaration + "\n" + "D - " + variable + "\n" + "E - " + expression
				 + "\n" + "F - " + operator);
		if(answer3.equals("D"))
			JOptionPane.showMessageDialog(null,"correct");
		else
			JOptionPane.showMessageDialog(null,"incorrect");
 
//introducing the new question
 
		JOptionPane.showMessageDialog(null,"what is a declaration");
		String answer4 = JOptionPane.showInputDialog("A - " + statement + "\n" +
				"B - " + comment + "\n" + "C - "  + 
				declaration + "\n" + "D - " + variable + "\n" + "E - " + expression
				 + "\n" + "F - " + operator);
		if(answer4.equals("C"))
			JOptionPane.showMessageDialog(null,"correct");
		else
			JOptionPane.showMessageDialog(null,"incorrect");
//introducing the new question
 
		JOptionPane.showMessageDialog(null,"what is an operator");
		String answer5 = JOptionPane.showInputDialog("A - " + statement + "\n" +
				"B - " + comment + "\n" + "C - "  + 
				declaration + "\n" + "D - " + variable + "\n" + "E - " + expression
				 + "\n" + "F - " + operator);
		if(answer5.equals("F"))
			JOptionPane.showMessageDialog(null,"correct");
		else
			JOptionPane.showMessageDialog(null,"incorrect");
//introducing the new question
 
		JOptionPane.showMessageDialog(null,"what is an expression");
		String answer6 = JOptionPane.showInputDialog("A - " + statement + "\n" +
				"B - " + comment + "\n" + "C - "  + 
				declaration + "\n" + "D - " + variable + "\n" + "E - " + expression
				 + "\n" + "F - " + operator);
		if(answer6.equals("E"))
			JOptionPane.showMessageDialog(null,"correct");
		else
			JOptionPane.showMessageDialog(null,"incorrect");
 
		// examples
 
		JOptionPane.showMessageDialog(null,"what is an example of a statement?");
		String example = ("int x = 3");
		String example2 = ("JTextArea outputArea");
		String example3 = (" // initializing");
		String example4 = ("output");
		String example5 = ("System.out.println();");
		String option = JOptionPane.showInputDialog("A - " + example + "\n" + "B - " + example2 +
				"\n" + "C - " + example3 + "\n" + "D - " + example4 + "\n" + "E - " + example5 + "\n");
		if(option.equals("E"))
			JOptionPane.showMessageDialog(null,"correct");
		else
			JOptionPane.showMessageDialog(null,"incorrect");
 
// examples
 
		JOptionPane.showMessageDialog(null,"what is an example of a comment?");
 
		String option2 = JOptionPane.showInputDialog("A - " + example5 + "\n" + "B - " + example2 +
				"\n" + "C - " + example3 + "\n" + "D - " + example4 + "\n" + "E - " + example);
		if(option2.equals("C"))
			JOptionPane.showMessageDialog(null,"correct");
		else
			JOptionPane.showMessageDialog(null,"incorrect");
 
// examples
 
		JOptionPane.showMessageDialog(null,"what is an example of a declaration?");
 
		String option3 = JOptionPane.showInputDialog("A - " + example5 + "\n" + "B - " + example2 +
				"\n" + "C - " + example3 + "\n" + "D - " + example4 + "\n" + "E - " + example);
		if(option3.equals("B"))
			JOptionPane.showMessageDialog(null,"correct");
		else
			JOptionPane.showMessageDialog(null,"incorrect");
// examples
 
		JOptionPane.showMessageDialog(null,"what is an example of a variable?");
 
		String option4 = JOptionPane.showInputDialog("A - " + example5 + "\n" + "B - " + example2 +
				"\n" + "C - " + example3 + "\n" + "D - " + example4 + "\n" + "E - " + example);
		if(option4.equals("D"))
			JOptionPane.showMessageDialog(null,"correct");
		else
			JOptionPane.showMessageDialog(null,"incorrect");
// examples
 
		JOptionPane.showMessageDialog(null,"what is an example of an expression?");
 
		String option5 = JOptionPane.showInputDialog("A - " + example5 + "\n" + "B - " + example2 +
				"\n" + "C - " + example3 + "\n" + "D - " + example4 + "\n" + "E - " + example);
		if(option5.equals("A"))
			JOptionPane.showMessageDialog(null,"correct");
		else
			JOptionPane.showMessageDialog(null,"incorrect");
		JOptionPane.showMessageDialog(null,"Congratulations! you made it past chapter 1");
break;
		case 2:
			String frame = ""; 
			TextArea lt;
			Button lesson1 = new Button("lesson 1");
			Button exit = new Button("exit");
			Button lesson2 = new Button("lesson 2");
			Button lesson3 = new Button("lesson 3");
			Button lesson4 = new Button("lesson 4");
			Button lesson5 = new Button("lesson 5");
			Button lesson6 = new Button("lesson 6");
			Button lesson7 = new Button("lesson 7");
			Button lesson8 = new Button("lesson 8");
			Button lesson9 = new Button ("lesson 9");
			Button lesson10 = new Button("lesson 10");
			String output =("memorize this frame as your lesson 1, " +
					"which is the start of all c++ programs") +
			 ("\n\n\n #include <iostream>\n") + ("#include <cstdio>") + ("\n#include <cstdlib>")
			 + ("\n using namespace std;") + ("\nint main(int nNumberofArgs, char* pczArgs[]){");
			JOptionPane.showConfirmDialog(null, output);
			JOptionPane.showMessageDialog(null,"now you try");			
		lt = new TextArea(frame,20,80);
 
		add(lt);
		add(lesson1);
		add(exit);	
		add(lesson2);
		add(lesson3);
		add(lesson4);
		add(lesson5);
		add(lesson6);
		add(lesson7);
		add(lesson8);
		add(lesson9);
		add(lesson10);
		String output2 	= ("Now learn how to close a program!");
		System.out.println(output2);
 
	}
	}
		// button action event
	public boolean action(Event evt, Object arg){
 
		String output = ("memorize this frame and write it, which is the start of all c++ programs") +
		 ("\n\n\n #include <iostream>\n") + ("#include <cstdio>") + ("\n#include <cstdlib>")
		 + ("\n using namespace std;") + 
		 ("\nint main(int nNumberofArgs, char* pczArgs[ ]){");	
		String output2 = "Now learn how to end a program \n\nLearn this, memorize it, now write it!" 
			+ "\n\n\nSystem(pause);" + "\nreturn 0;";
		String output3 = "A computer needs to know what kind of variable the user is using to process" +
		"\nthe program. The kind of variables are expressed by type. In other words, a type is just an identification marker." +
		"\nTherefore, the most common type for words is String. So, initilizing a string " +
		"\nwould look like String sEric.\n\nnow you try initializing your name.";
		String output4 = "The most common type for numbers is double because double can represent fractions and whole numbers." +
				" \nSo, here is an exampleof a double:\n\ndouble 2.5. \nnow you try writing a double. Type int is used for integers, example:" +
				"\n\nint 2";
		String output5 = "A less common type is character. This is used for single letters like a,b,c, etc. \n Example is: \n\nchar d.";
		String output6 = "When you tell the computer to do a command, it will show as something like this: \n\ncout<< type your name;" + 
		"\n\nor int nAge; \n//(declaration) \n\ncin>> int nAge; \n//(this is where the user inputs his age) " +
		"\n\ncout<< Eric is nAge; \n//(statement) + result is: \n//31" + "\n\nnow you try telling the computer to output your age or weight or height";
		String output7 = "When you tell a user to input a command, it looks like:" + "\nint nAge;" +
				" \ncin>> int nAge;\n\n//(this is where the user inputs his age and stays in the computer's memory)" + "\nnow you try telling a user"
				+ "to input his grade point average";
		String output8 = "now write the frame and tell the computer to output that I love my mom and write the end frame. \nIt should look like this:" +
		"\n\n#include<iostream>\n#include<cstdlib>\n#include<cstdio>\nusing namespace std;\nint main(int nNumberofArgs, char* pczArgs[]{" + 
		"\ncout<<I love my mom;\nSystem(pause);\nreturn 0;\n}";
		String output9 = "a brace ({) must always be closed at some point(}). a statement must always end with a semicolon(;). ";
		String output10 = "congratulations! you are finished with chapter 2!" + "\n I am very proud of you!";
 
		if (evt.target instanceof Button){
			String label = (String)arg;
			if ( label.equals("lesson 1"))
			JOptionPane.showMessageDialog(null,output);
 
 
		else{
				if(label.equals("exit"))
					System.exit(0);		
 
		else	{
 
		if(label.equals("lesson 2"))
 
			JOptionPane.showMessageDialog(null,output2);			
 
		else{
		if(label.equals("lesson 3"))
					JOptionPane.showMessageDialog(null,output3);
		else{
			if(label.equals("lesson 4"))
				JOptionPane.showMessageDialog(null,output4);
			else{
				if(label.equals("lesson 5"))
					JOptionPane.showMessageDialog(null,output5);
				else{
					if(label.equals("lesson 6"))
						JOptionPane.showMessageDialog(null,output6);
					else{
						if(label.equals("lesson 7"))
							JOptionPane.showMessageDialog(null,output7);
						else{
							if(label.equals("lesson 8"))
								JOptionPane.showMessageDialog(null,output8);
							else{
								if(label.equals("lesson 9"))
									JOptionPane.showMessageDialog(null,output9);
								else{
									if(label.equals("lesson 10"))
										JOptionPane.showMessageDialog(null,output10);
		}
		}
		}
		}
		}
		}
		}
	}
		}
		}
		}
	return true;	
			}	
case 3:
}
 
}