Java questions Tasks You are required to write three Java classes: Term.java For
ID: 3685382 • Letter: J
Question
Java questions
Tasks
You are required to write three Java classes:
Term.java
Formula.java
Equation.java
Each link above gives you a skeleton of the required class, including instance variables, a constructor, and several methods. You are required to complete the constructors and methods whose bodies are marked with the comment TODO. Note that where a TODO method has a non-void return-type, it has a dummy return statement to allow the partially-written class to compile: you should delete that return statement when you write that method. Make sure you understand the connections between the various classes.
Term.Java
/**
* Term represents terms in a chemical formula
* Only elements denoted by a single letter are supported
*
* Examples: N, H2, C20, H147
*
* @author
* @version
*/
public class Term
{
private char element;
private int atoms;
// creates a Term with the provided values
public Term(char element, int atoms)
{
this.element = element;
this.atoms = atoms;
}
// creates a Term by parsing s
// e.g. "H20" would give element = 'H', atoms = 20
public Term(String s)
{
// TODO
}
// turns the Term into a String
// e.g. element = 'C', atoms = 4 would give "C4"
public String display()
{
// TODO
return "";
}
// returns the current value of element
public char getElement()
{
return element;
}
// returns the current value of atoms
public int getAtoms()
{
return atoms;
}
}
Formula.java
/**
* Formula represents chemical formulae
* e.g. Hexane:
Structural formula CH3CH2CH2CH2CH2CH3
Molecular formula C6H14
*
* In a molecular formula, elements are listed only once, and they are listed alphabetically
*
* @author
* @version
import java.util.ArrayList;
public class Formula
{
private ArrayList<Term> terms;
// creates a Formula with the provided value
public Formula(ArrayList<Term> terms)
{
this.terms = terms;
}
// creates a Formula by parsing s
// e.g. "CH2O" would give terms = {Term('C',1),Term('H',2),Term('O',1)}
public Formula(String s)
{
// TODO
}
// returns the index of the rightmost upper-case letter in s, or -1 if none found
// e.g. "COHOHH2" would give 5
public static int lastElement(String s)
{
// TODO
return -2;
}
// turns the Formula into a String
// e.g. terms = {Term('C', 1),Term('O',2)} would give "CO2"
public String display()
{
// TODO
return "";
}
// returns the current value of terms
public ArrayList<Term> getTerms()
{
return terms;
}
// changes terms into molecular form
// e.g. terms = {Term('H',3),Term('C',1),Term('H',3),Term('C',1)} would become {Term('C',2),Term('H',6)}
public void makeMolecular()
{
// TODO
}
// returns the next element in terms, alphabetically
// e.g. terms = {Term('H',4),Term('C',2),Term('H',4),Term('C',1)} would return Term('C',2)
public Term nextElement()
{
// TODO
return null;
}
// returns true iff f is identical to this Formula
// e.g. terms = {Term('C',2),Term('H',6)} and f = {Term('C',2),Term('H',6)} would return true
// but terms = {Term('C',2),Term('H',6)} and f = {Term('H',6),Term('C',2)} would return false
public boolean identical(Formula f)
{
// TODO
return false;
}
// returns true iff f is an isomer of this Formula
// e.g. terms = {Term('C',2),Term('H',6)} and f = {Term('C',1),Term('H',3),Term('C',1),Term('H',3)}
// would return true
public boolean isomer(Formula f)
{
// TODO
return false;
}
}
Equation.java
/**
* Equation represents chemical equations
* It allows only single molecules atm, i.e. "O+H2=H2O" is fine,
* but "O+2H=H2O" is illegal, and would have to be written "O+H+H=H20"
*
* @author
* @version
*/
import java.util.ArrayList;
public class Equation
{
private ArrayList<Formula> lhs, rhs;
// creates an Equation with the provided values
public Equation(ArrayList<Formula> lhs, ArrayList<Formula> rhs)
{
this.lhs = lhs;
this.rhs = rhs;
}
// creates an Equation by parsing s
// e.g. "O+H2=H2O" would give
// lhs = {Formula({Term('O',1)}), Formula({Term('H',2)})},
// rhs = {Formula({Term('H',2), Term('O',1)})}
public Equation(String s)
{
// TODO
}
// returns a parsed form of one side of an equation
// e.g. "O+H2" would return {Formula({Term('O',1)}), Formula({Term('H',2)})}
public static ArrayList<Formula> parseSide(String s)
{
// TODO
return null;
}
// turns the Equation into a String
// e.g. lhs = {Formula({Term('O',1)}), Formula({Term('H',2)})},
// rhs = {Formula({Term('H',2), Term('O',1)})}
// would return "O + H2 = H2O"
public String display()
{
// TODO
return "";
}
// returns true iff this Equation specifies the same atom-counts on each side
// e.g. lhs = {Formula({Term('O',1)}), Formula({Term('H',2)})},
// rhs = {Formula({Term('H',2), Term('O',1)})}
// would return true
public boolean balanced()
{
// TODO
return false;
}
// returns the current value of lhs
public ArrayList<Formula> getLHS()
{
return lhs;
}
// returns the current value of rhs
public ArrayList<Formula> getRHS()
{
return rhs;
}
}
Explanation / Answer
Term.java:
public class Term
{
private char element;
private int atoms;
// creates a Term with the provided values
public Term(char element, int atoms)
{
this.element = element;
this.atoms = atoms;
}
// creates a Term by parsing s
// e.g. "H20" would give element = 'H', atoms = 20
public Term(String s)
{
element = s.charAt(0);
if (s.length() == 1)
atoms = 1;
else
atoms = Integer.parseInt(s.substring(1));
}
// turns the Term into a String
// e.g. element = 'C', atoms = 4 would give "C4"
public String display()
{
String s = "" + element;
if (atoms > 1) s += atoms;
return s;
}
// returns the current value of element
public char getElement()
{
return element;
}
// returns the current value of atoms
public int getAtoms()
{
return atoms;
}
}
Formula.java:
import java.util.ArrayList;
public class Formula
{
private ArrayList<Term> terms;
// creates a Formula with the provided value
public Formula(ArrayList<Term> terms)
{
this.terms = terms;
}
// creates a Formula by parsing s
// e.g. "CH2O" would give terms = {Term('C',1),Term('H',2),Term('O',1)}
public Formula(String s)
{
terms = new ArrayList<> ();
int k = lastElement(s);
terms.add(new Term(s.substring(k)));
while (k > 0)
{
int j = lastElement(s.substring(0, k));
terms.add(0, new Term(s.substring(j, k)));
k = j;
}
}
// returns the index of the rightmost upper-case letter in s, or -1 if none found
// e.g. "COHOHH2" would give 5
public static int lastElement(String s)
{
for (int k = s.length() - 1; k >= 0; k--)
if (Character.isUpperCase(s.charAt(k)))
return k;
return -1;
}
// turns the Formula into a String
// e.g. terms = {Term('C', 1),Term('O',2)} would give "CO2"
public String display()
{
String s = "";
for (Term t : terms) s += t.display();
return s;
}
// returns the current value of terms
public ArrayList<Term> getTerms()
{
return terms;
}
// changes terms into molecular form
// e.g. terms = {Term('H',3),Term('C',1),Term('H',3),Term('C',1)} would become {Term('C',2),Term('H',6)}
public void makeMolecular()
{
ArrayList<Term> z = new ArrayList<>();
Term t, u;
while (terms.size() > 0)
{
t = nextElement();
terms.remove(t);
if (z.isEmpty() || t.getElement() != z.get(z.size() - 1).getElement())
z.add(t);
else
{
u = new Term(t.getElement(), t.getAtoms() + z.get(z.size() - 1).getAtoms());
z.remove(z.size() - 1);
z.add(u);
}
}
terms = z;
}
// returns the next element in terms, alphabetically
// e.g. terms = {Term('H',4),Term('C',2),Term('H',4),Term('C',1)} would return Term('C',2)
public Term nextElement()
{
Term z = terms.get(0);
for (Term x : terms)
if (x.getElement() < z.getElement())
z = x;
return z;
}
// returns true iff f is identical to this Formula
// e.g. terms = {Term('C',2),Term('H',6)} and f = {Term('C',2),Term('H',6)} would return true
// but terms = {Term('C',2),Term('H',6)} and f = {Term('H',6),Term('C',2)} would return false
public boolean identical(Formula f)
{
if (this.getTerms().size() != f.getTerms().size())
return false;
for (int k = 0; k < this.getTerms().size(); k++)
if (this.getTerms().get(k).getElement() != f.getTerms().get(k).getElement() ||
this.getTerms().get(k).getAtoms() != f.getTerms().get(k).getAtoms())
return false;
return true;
// Alternatively, the following would do it:
// return this.display().equals(f.display());
}
// returns true iff f is an isomer of this Formula
// e.g. terms = {Term('C',2),Term('H',6)} and f = {Term('C',1),Term('H',3),Term('C',1),Term('H',3)}
// would return true
public boolean isomer(Formula f)
{
this.makeMolecular();
f.makeMolecular();
return this.identical(f);
}
}
Equation.java:
import java.util.ArrayList;
public class Equation
{
private ArrayList<Formula> lhs, rhs;
// creates an Equation with the provided values
public Equation(ArrayList<Formula> lhs, ArrayList<Formula> rhs)
{
this.lhs = lhs;
this.rhs = rhs;
}
// creates an Equation by parsing s
// e.g. "O+H2=H2O" would give
// lhs = {Formula({Term('O',1)}), Formula({Term('H',2)})},
// rhs = {Formula({Term('H',2), Term('O',1)})}
public Equation(String s)
{
int eq = s.indexOf('=');
lhs = parseSide(s.substring(0, eq));
rhs = parseSide(s.substring(eq + 1));
}
// returns a parsed form of one side of an equation
// e.g. "O+H2" would return {Formula({Term('O',1)}), Formula({Term('H',2)})}
public static ArrayList<Formula> parseSide(String s)
{
ArrayList<Formula> side = new ArrayList<>();
int plus = s.indexOf('+');
while (plus >= 0)
{
side.add(new Formula(s.substring(0, plus)));
s = s.substring(plus + 1);
plus = s.indexOf('+');
}
side.add(new Formula(s));
return side;
}
// turns the Equation into a String
// e.g. lhs = {Formula({Term('O',1)}), Formula({Term('H',2)})},
// rhs = {Formula({Term('H',2), Term('O',1)})}
// would return "O + H2 = H2O"
public String display()
{
String sl = "";
for (Formula f : lhs)
sl += " + " + f.display();
String sr = "";
for (Formula f : rhs)
sr += " + " + f.display();
return sl.substring(3) + " = " + sr.substring(3);
}
// returns true iff this Equation specifies the same atom-counts on each side
// e.g. lhs = {Formula({Term('O',1)}), Formula({Term('H',2)})},
// rhs = {Formula({Term('H',2), Term('O',1)})}
// would return true
public boolean balanced()
{
ArrayList<Term> l = new ArrayList<>();
for (Formula f : lhs)
l.addAll(f.getTerms());
ArrayList<Term> r = new ArrayList<>();
for (Formula f : rhs)
r.addAll(f.getTerms());
return (new Formula(l)).isomer(new Formula(r));
}
// returns the current value of lhs
public ArrayList<Formula> getLHS()
{
return lhs;
}
// returns the current value of rhs
public ArrayList<Formula> getRHS()
{
return rhs;
}
}
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