****************6.0 Method********************************
******************************************************

import java.util.*;

class Main {
  public static 
  Scanner in=  new Scanner( System.in );
  
  public static 
  void main(String[] args) {
  	
  	int start, finish;
  	int total;
  	
  	say( "Compute the sum of integers within a range.");

  	start=  ask( "What is the start of the range?" );
  	finish=  ask( "What is the end of the range?  " );

	total=  addRange( start, finish );
	
	say( "The (inclusive) sum is", total );
  }
  
  // Method to read input (after prompting).  //
  public static 
  int ask( String s ) {
	int result;
  	System.out.print( s );
  	result=  in.nextInt();
  	return result;
  }

  // Method to display a message. //
  public static 
  void say( String s ) {
  	System.out.println( s );
  }
  // Method to display a message  & a value. //
  public static 
  void say( String s, int j ) {
  	System.out.println( s + " " + j );
  }
  
  // Method to add up a range. //
  public static 
  int addRange( int first, int last ) {
  	int result=0;
  	
  	for (int j=first; j<=last; ++j ) {
  		// Add the next number to the total.
  		result += j;
  	}
  	return result;
  }
  
}



****************integer divisions********************************
******************************************************

class Main {
  public static void main(String[] args) {

	//// FLOAT EXPRESSIONS

	say( "		5/3" );
	say( "5.0/3.0 is "	+ 5.0/3.0 );
	say( "5/3.0 is " 	+ 5/3.0 );
	say( "5.0/3 is "	+ 5.0/3 );

	say( "		2/3" );
	say( "2.0/3.0 is "	+ 2.0/3.0 );
	say( "2/3.0 is " 	+ 2/3.0 );
	say( "2.0/3 is "	+ 2.0/3 );

	say( "		1/3" );
	say( "1.0/3.0 is "	+ 1.0/3.0 );
	say( "1/3.0 is " 	+ 1/3.0 );
	say( "1.0/3 is "	+ 1.0/3 );

	say( "		1/3 + 2/3" );
	say( "1.0/3.0 + 2.0/3.0 is "	+  (1.0/3.0 + 2.0/3.0)  );

	
	////  INTEGER EXPRESSIONS:
	say( "\nNow, try this with integer division!" );
	say( "5/3 is	"	+ 5/3 );
	say( "2/3 is	"	+ 2/3 );
	say( "1/3 + 2/3 is " + 1/3 + 2/3 );


	say( "\nFractions only." );
	say( (5%3)/3.0 );
	say( 5.0%3 / 3 );
	say( 5/3 + 5.0%3 / 3 );
	
	

	//// EXAMPLE.  Illustrates why you should never compare floats (or doubles).

	say( "\nNever compare floats (or doubles)." );
	example();
  }
  
  
  
  //// METHODS ////
  static void example() 	{

	say( "	a=  5 / 3.;" );
	say( "	b=  1 + 2 /3.;" );
	say( "	// 5/3 should be the same as 1+2/3");

	double a, b;
	a=  5 / 3. ;
	b=  1 + 2 /3. ;
	
	say( "a is ", a );
	say( "b is ", b );
	
	say( "	if (a == b)		// equal"  );
	say( "	else			// unequal"  );
	
	if (a == b)	say( "Both are equal.");
	else		say( "These values are unequal.");
	
  }
  
  
  //// I/O METHODS ////
  static void say( String s ) {		// Display a String
  	System.out.println( s );
  }
  static void say( double x ) {		// Display a double
  	System.out.println( x );
  }
  static void say( String s, double x ) {		// Display string & value
  	System.out.println( s +" "+ x );
  }
  
}


****************6.2********************************
******************************************************

//// c6.2:  Sum the digits (using a method.)
import java.util.*;

class Main {
	public static Scanner r=  new Scanner( System.in );
	
  // Main method. //	
  public static void main(String[] args) {
  	
  	int number, total;
  	double a;
  	int lastDigit;

  	do {

	  	a=  ask( "\nEnter the next number:  ");
  		number=  (int) a ;					// Convert to integer.

  		if (number ==0) break;
  		if (number < 0) {
  			say( "DON'T BE SO NEGATIVE!" );
  			continue;
  		}
  		
		total=  sumDigits( number );
  		say( "Sum of the digits is:    " + total );
  		
  		lastDigit=  number % 10;
		System.out.println( "Last digit is:    " + lastDigit );
  		
  		//// Check divisibility.
  		if (lastDigit % 2 == 0) say( number + " is even" );
  		if (total % 3 == 0) say( "Divisible by 3." );
  		if (lastDigit == 0  || lastDigit == 5) say( "Divisible by 5.");

  		if ( isFactor( 7, number )) say( "Divisible by 7." );

		int j=11;
  		if ( isFactor( j, number )) say( "Divisible by " + j );

		j=j+2;
  		if ( isFactor( j, number )) say( "Divisible by " + j );

		j=j+2;
		j=j+2;
  		if ( isFactor( j, number )) say( "Divisible by " + j );

		j=j+2;
  		if ( isFactor( j, number )) say( "Divisible by " + j );

		j=j+2;
		j=j+2;		// 23
  		if ( isFactor( j, number )) say( "Divisible by " + j );

		j=j+2;
		j=j+2;
		j=j+2;		// 29
  		if ( isFactor( j, number )) say( "Divisible by " + j );

		j=j+2;
  		if ( isFactor( j, number )) say( "Divisible by " + j );

		j=j+2;
		j=j+2;
		j=j+2;		// 37
  		if ( isFactor( j, number )) say( "Divisible by " + j );

		if (number > 1000) say( "> 1000" );

  	} while( number != 0 );
  	// Exit loop if zero is entered. //

	say( "DONE" );
	return;


  }// END OF main method. //
  
  
  // I/O methods. //
  public static void say( String s ) {
	System.out.println( s );
  }
  public static double ask( String s ) {
	System.out.print( s );
	return r.nextDouble( );
  }
  
  
  // Return the sum of the digits. //
  public static int sumDigits( int n ) {
  	int sum=0;
  	
  	while (n > 0) {
  		
  		sum += n % 10;		// Last digit of Number
  		sum = sum + n % 10;		// Last digit of Number
  		
  		n /=  10;			// Throw away last digit.\!
  		n=  n / 10;			// Throw away last digit.\!

  	}

  	return sum;
  }// END OF sumDigits() method. //


  // Return true if f is a factor of n.  //
  public static boolean isFactor( int f,  int n ) {
  	boolean result;
  	if (n % f == 0) {
  		result=true;
  	}
  	else{
  		result=false;
  	}
  	return result;
  }// END OF isFactor() method. //

  // Return true if f is a factor of n.  //
  public static boolean isFactor1( int f,  int n ) {
  	 return (n % f == 0);
  }// END OF isFactor() method. //


  // Return true if f is a factor of n.  //
  public static boolean isFactor2( int f,  int n ) {
  	boolean result;
  	result = (n % f == 0) ? true : false;
  	return result;
  }// END OF isFactor() method. //


  // Return true if f is a factor of n.  //
  public static boolean isFactor3( int f,  int n ) {
  	boolean result=false;
  	if (n % f == 0) result=true;
  	return result;
  }// END OF isFactor() method. //



  
}// END OF class Main. //


****************6.2********************************
******************************************************

//// c6.2:  Sum the digits (using a method.)
//// Zhilin Kuang

import java.util.Scanner;
class Main {
	
  // Main method. //	
  public static void main(String[] args) {
  	int sum;
    Scanner input = new Scanner (System.in);
	// ADD INPUT CODE HERE //
    System.out.print("Please enter a number:  ");
    int n1= input.nextInt ();
    
    sum=  sumDigits( n1 );
    
    System.out.println( "The sum of the digits is:  " + sum );
    
  }// END OF main method. //
  
  // Return the sum of the digits. //
  public static int sumDigits( int n1) {
  	int result=0, remainder=0; 
  	for ( int n = n1; n>0; n=n/10 )
  	remainder += n % 10 ;
  	result += remainder;
  	return result;
  	//return remainder;
  }// END OF sumDigits() method. //
  
}// END OF class Main. //


****************6.3********************************
******************************************************

////6.3: Palindrome & reverse
////Author: Zhilin Kuang

import java.util.Scanner;

class Main {
  public static void main(String[] args) {
    Scanner input = new Scanner (System.in);
    int n, N;
    System.out.print ("Enter an integer: ");
    n= input.nextInt ();
    System.out.print ("The reverse of this integer is: ");
    N=reverse (n);
    System.out.print (N);
    if (n==N) {
    	System.out.println ( "\n"+ n + " is a palindrome.");
    }
    else {
    	System.out.println ( "\n"+ n + " is NOT a palindrome."); 
    }
 }
  //Deserted loop method
  /*public static void reverse (int n) {
  	while (n!=0){
  		int remainder= n%10;
  		System.out.print (remainder);
  		n=n/10;
  	}*/
  	
  //I replaced the void method with a returnValue method.	
  public static int reverse (int n){
  	int result = 0;
  	for (int a=n; a>0; a/=10){
  	result = (result*10) + (a % 10);
  	}
  	return result;
  }
}


****************6.5********************************
******************************************************


import java.util.Scanner;

class Main {
  public static void main(String[] args) {
    System.out.print("Enter 3 different numbers:");
    Scanner input = new Scanner (System.in);
    double n1,n2,n3,temp=0,temp2=0;
    n1= input.nextDouble();
    n2= input.nextDouble();
    n3= input.nextDouble();
    if (n1<n2) {
    	//n1<n2<n3
    	if (n2<n3){
    	  n1=n1;
    	  n2=n2;
    	  n3=n3;}
    	//n3<n1<n2
    	else if (n3<n1){
    	  temp=n1;
    	  temp2=n2; 
    	  n1=n3;
    	  n2=temp;
    	  n3=temp2;}
    	//n1<n3<n2
    	else {
    	  temp=n2;
    	  n2=n3;
    	  n3=temp;
    	  n1=n1;
    	}  
    }
    //n1>n2
    else {
    	//n1>n2>n3
    	if (n2>n3){
    		n2=n2;
    		temp=n3;
    		n3=n1;
    		n1=temp;
    	}
    	//n3>n1>n2
    	else if(n3>n1){
    		temp=n1;
    		n3=n3;
    		n1=n2;
    		n2=temp;
    	}
    	//n1>n3>n2
    	else {
    		temp=n1;
    		temp2=n2;
    		n2=n3;
    		n1=temp2;
    		n3=temp;
    	}
    }
    System.out.println( n1 + "<" +n2 + "<" + n3);
    System.out.println( "The median of these 3 numbers is: " + n2);
  }
}


****************5.12********************************
******************************************************

//Excercise 5.12 Find the smallest n such that n^2 > 12000
//Author: Zhilin Kuang

class Main {
  public static void main(String[] args) {
    int n=0;
    while (Math.pow(n,2) <=12000){
      n++;	
    }
    System.out.println ("The number is " + n);
  }
}


****************5.13********************************
******************************************************

//Excercise 5.13 Find the largest n such that n^3 < 12000
//Author: Zhilin Kuang

class Main {
  public static void main(String[] args) {
    int n=12000;
    while (Math.pow(n,3) >12000){
      n--;	
    } 
    System.out.println ("The number is " + n);
  }
}


****************while loop********************************
******************************************************

//// List all factors of a number and tell if it is a prime.
//// CST 112:  Zhilin

import java.util.Scanner;

class Main {
	
 public static void main(String[] args) {

  Scanner in = new Scanner(System.in);
  int n, f, i;
  boolean prime;
    
    do{
        /* I a scratching out all these codes below.
        System.out.print( "\nFactor Check \nEnter an interger:  ");
        i=in.nextInt();
        System.out.print( "Enter a potential factor: ");
        f=in.nextInt();
	  	if ( isFactor(i, f) )
	  	{
  			System.out.println( f + " is a factor of " + i );
	  	}
	  	else {
	  		System.out.println( f + " is NOT a factor of " + i );
	  	}*/
  	
  	    // Code starts here. //
  		// Read a number and list its factors. //
		System.out.print( "\nEnter the next number: ");
  		n=  in.nextInt();
  		System.out.print ("The factors of "+n+ " are:  ");
  		/*If number is prime, prompt message there's no factors that's not 1 and itslef.*/
  		if (prime (n)){
  		    System.out.print (n+" does not have factors other than 1 and itself.");	
  		}
  		
  		//If number is not prime, loop to list factors//
  		else{ 
  		    f=n;
  		    while ( f>1) {
  			    f--;
  		    	if (n%f == 0 && f!=1) {
  				   System.out.print (f + " ");
  		    	} 
  		    } 
     	}
  		// Tell if the number is prime. //
  		if ( prime(n) ) {
  			System.out.println( "\n"+n +" is a prime number." );
  		}
		else {
			System.out.println( "\n"+n +" is NOT a prime number." );
		}
    } while (n!=0);
  }
  
  // I commented out my isFactor method. It doesn't seem like I still need it.
  //// Return true iff the first argument ("factor") is a factor of the second number.
  /*public static boolean isFactor( int a,  int b ) {
  	boolean result;
  	if (a % b == 0) {
  		result=true;
  	}
  	else{
  		result=false;
  	}
  	return result;
  }*/
  
  public static boolean prime ( int a ) {
  	boolean result;
  	int f=a, n=0;
  	while ( f>1) {
  			f--;
  			if (a%f == 0) {
  				n+=f;
  			} 
  		} 
  	if (n>1||a==0) {
  		result=false;
  	}
  	else{
  		result=true;
  	}
  	return result;
  }
 
}


****************for loop********************************
******************************************************

//// List all factors of a number and tell if it is a prime.
//// CST 112:  Zhilin Kuang

import java.util.Scanner;

class Main {
	
 public static void main(String[] args) {

  Scanner in = new Scanner(System.in);
  int n;
  boolean prime;
  
  do {
     // Read a number. //
	 System.out.print( "\nEnter the next number: "  );
  	 n=in.nextInt();
     
     // List factors. //
  	 if (findFactor (n)){
  	    System.out.println ("are factors of " + n);	
  	 }
  	 // Tell number is prime. //
   	 else {
   	 	//Check for 0 first. //
   	 	if (n==0) {
   	 		System.out.println( n + " is NOT a prime number, all real numbers are factors of 0." );
   	 	}
   	 	else {
   	 	    System.out.println( n + " is a prime number." );	
   	 	}
  	 }
   } while (n!=0);
  }
  
  //// Return true iff the first argument ("factor") is a factor of the second number.
  public static boolean isFactor( int factor, int number ) {
  	boolean result;
  	if (number % factor == 0) {
  		result=true;
  	}
  	else{
  		result=false;
  	}
  	return result;
  }
  
  // Loop to list the factors and check if number is prime. //
  public static boolean findFactor (int n) {
  	boolean result=false;
  	for (int j=n-1; j>1; j--){
  		if ( isFactor(j, n) ){
		  	System.out.print( j + " " );
		  	result=true;
	  	}
  	}
  	return result;
  }
 
}

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****************SEP 12********************************
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