// City program for ISM001 homework 2import java.util.Scanner;public class City { //---------------------------- // Attributes of the city: //---------------------------- private String name="My City"; private int population=500; private int wealth=population; //---------------------------- // Constructors //---------------------------- public City( String name ){ this.name = name; } public City( String name, int population ){ this(name); this.population = population; } public City( String name, int population, int wealth ){ this(name, population); this.wealth = wealth; } //---------------------------- // Get methods //---------------------------- public String toString(){ return name; } public int getPopulation(){ return population; } public int getWealth(){ return wealth; } //---------------------------- // Change the attributes // (another form of set methods) //---------------------------- // Add citizens to the city // When n < 0, it will remove citizens. // It will also guarantee that population will not be negative. public void addPopulation(int n){ population += (population + n > 0)? n: (-population); } // Add n units of wealth to the city public void addWealth(int n){ wealth += n; } //---------------------------- // Check the attributes //---------------------------- // Check if the city is empty public boolean isEmpty(){ return (population<=0); } // Check if there is any debt public boolean isDebit(){ return (wealth<0); } //---------------------------- // Events //---------------------------- // Earthquake public void earthquake(){ addPopulation( (int)(getPopulation() * -.8) ); addWealth(-1000); } // Trade with city c public boolean tradeWith( City c ){ if(!isEmpty() && !c.isEmpty() && !c.isDebit()){ addWealth(500); addPopulation(100); c.addWealth(500); c.addPopulation(100); return true; } return false; } //---------------------------- // Other methods //---------------------------- public void displayMessage(){ System.out.printf("%s (%d, %d)\n", toString(), getPopulation(), getWealth()); } //-------------------------------------- // Main program to test the code //-------------------------------------- public static void main( String args [] ){ City city[] = { new City("Hong Kong"), new City("Macau", 50), new City("Shanghai", 2000, 1000) }; // Initial System.out.println("\nInitial:"); for( City c: city ) c.displayMessage(); // Events: System.out.println("\nAfter some events:"); city[0].tradeWith(city[2]); city[1].earthquake(); city[2].earthquake(); for( City c: city ) c.displayMessage(); // More changes: System.out.println("\nAfter some more changes"); city[0].addPopulation(200); city[1].addPopulation(-100); city[2].addPopulation(300); city[2].addWealth(-1400); for( City c: city ) c.displayMessage(); for( City c: city ){ if( c.isEmpty() ) System.out.printf("There are no more citizens in %s!\n", c); if( c.isDebit() ) System.out.printf("%s is in debt!\n", c); } } }