Question

ok so my assignment I’m supposed to write a class that stores a temperature that the user gives and checks it with the set parameters to see if Ethy/Oxygen/Water are either freezing or boiling and then display it at the end which ones will be freezing/boiling at the temperature that they entered. I have the majority of both the class and tester completed but I’m getting several errors on my code. I’m not asking anyone to give me the answer but if you could tell me what I’m doing wrong I would greatly appreciate it. Here is my code for class:

public class FreezingBoilingPoints {

    private int temperature;

    public FreezingBoilingPoints(int temp) {
        temperature = temp;
    }

    public void setTemperature(int temp) {
        temperature = temp;
    }

    public int getTemperature() {
        return temperature;
    }

    private Boolean isEthylFreezing(int temperature) {
        if (temperature <= -173) {
            return true;
        } else {
            return false;
        }
    }

    private Boolean isEthylBoiling(int temperature) {
        if (temperature >= 172) {
            return true;
        } else {
            return false;
        }
    }

    private Boolean isOxygenFreezing(int temperature) {
        if (temperature <= -362) {
            return true;
        } else {
            return false;
        }
    }

    private Boolean isOxygenBoiling(int temperature) {
        if (temperature >= -306) {
            return true;
        } else {
            return false;
        }
    }

    private Boolean isWaterFreezing(int temperature) {
        if (temperature <= 32) {
            return true;
        } else {
            return false;
        }
    }

    private Boolean isWaterBoiling(int temperature) {
        if (temperature >= 212) {
            return true;
        } else {
            return false;
        }
    }

    public String showTempinfo() {
        if (isEthylFreezing()) {
            System.out.println("Ethyl will freeze");
        }

        if (isEthylBoiling()) {
            System.out.println("Etheyl will boil");
        }

        if (isOxygenFreezing()) {
            System.out.println("Oxygen will freeze");
        }

        if (isOxygenBoiling()) {
            System.out.println("Oxygen will Boil");
        }

        if (isWaterFreezing()) {
            System.out.println("Water will freeze");
        }

        if (isWaterBoiling()) {
            System.out.println("Water will boil");
        }
    }
}

and the code for my tester is below:

import java.util.Scanner;

public class FreezingBoilingTester {
    public static void main(String[] args) {
        int temperature;

        FreezingBoilingPoints temp1 = new FreezingBoilingPoints(0);

        Scanner scan = new Scanner(System.in);
        System.out.println("Please enter a temperature: ");
        temperature = scan.nextInt();

        System.out.println(showTempinfo());
    }
}

Answer 1

1) don’t pass the temp inside methods, because you already have this value in member variable.

2) you can change if (condition) then true else false into return (condition) and it will be the same result, just for readability .

3) you should return boolean not Boolean wrapper until you need the wrapper.

public final class FreezingBoilingPoints {

    private int temperature;

    public FreezingBoilingPoints(int temp) {
        temperature = temp;
    }

    public void setTemperature(int temp) {
        temperature = temp;
    }

    public int getTemperature() {
        return temperature;
    }

    private boolean isEthylFreezing() {
        return (temperature <= -173);
    }

    private boolean isEthylBoiling() {
        return  (temperature >= 172);
    }

    private boolean isOxygenFreezing() {
        return (temperature <= -362);
    }

    private boolean isOxygenBoiling() {
        return (temperature >= -306);
    }

    private boolean isWaterFreezing() {
        return (temperature <= 32) ;
    }

    private boolean isWaterBoiling() {
        return (temperature >= 212);
    }

    public String showTempinfo() {
        StringBuilder result = new StringBuilder();

        if (isEthylFreezing()) {
            result.append("Ethyl will freeze");
            result.append("\n");
        }

        if (isEthylBoiling()) {
            result.append("Etheyl will boil");
            result.append("\n");
        }

        if (isOxygenFreezing()) {
            result.append("Oxygen will freeze");
            result.append("\n");
        }

        if (isOxygenBoiling()) {
            result.append("Oxygen will Boil");
            result.append("\n");
        }

        if (isWaterFreezing()) {
            result.append("Water will freeze");
            result.append("\n");
        }

        if (isWaterBoiling()) {
            result.append("Water will boil");
            result.append("\n");
        }

        return result.toString();
    }
}

Main:

import java.util.Scanner;

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

    Scanner scan = new Scanner(System.in);
    System.out.println("Please enter a temperature: ");
    int temperature = scan.nextInt();

    FreezingBoilingPoints temp1 = new FreezingBoilingPoints(temperature );
    System.out.println(temp1.showTempinfo());
  }
}

updated:
you can use String concatenation:

String result = "";

if ( condition ) {
  result += "new result";
  result += "\n";
}

but this is not recommended in term of performance, because each += operation will create another String object in memory holding the new result.