I'm writing a program that converts certain units and I keep encountering errors. My program has 4 methods (one for the original unit, one to convert to the new unit, one for the conversion & one for how many units) as you can tell and each method is written correctly. When I ran it, I got the error of "unresolved compilation problem."

Here's the code:

```
public static String getUnitFrom(){
    String original = "";

    final String OZ = "oz";
    final String LB = "lb";
    final String IN = "in";
    final String FT = "ft";

    switch(original){
    case OZ:
        original = "oz";
        break;
    case LB:
        original = "lb";
        break;
    case IN:
        original = "in";
        break;
    case FT:
        original = "ft";
        break;
    default:
        System.out.println("Invalid input.");
    }
    return original;    

}

public static String getUnitTo(String conversionFromUnit){
    String conversionFromUnit = "";
    final String G = "g";
    final String KG = "kg";
    final String MM = "mm";
    final String CM = "cm";
    final String M = "m";

    if(getUnitFrom().equals("oz") || getUnitFrom().equals("lb")){
        switch(conversionFromUnit){
        case G:
            conversionFromUnit = "g";
            break;
        case KG:
            conversionFromUnit = "kg";
            break;
        default:
            System.out.println("Invalid conversion!");
        }
    }
    else if (getUnitFrom().equals("in") || getUnitFrom().equals("ft")){
        switch (conversionFromUnit){
        case MM:
            conversionFromUnit = "mm";
            break;
        case CM:
            conversionFromUnit = "cm";
            break;
        case M:
            conversionFromUnit = "m";
            break;
        default:
            System.out.println("Invalid conversion!");
        }
    }
    return conversionFromUnit;
}
public static double getValue(){
    double value = 0;

    if(getUnitFrom() > 0 && getUnitTo() > 0){
        value = input.nextDouble();
    }

}
public static double getConversionRate(String from, String to){
    double rate = 0;

    if(from.equals(getUnitFrom("oz")) && to.equals(getUnitTo("g"))){
        rate = 28.3;
    }
    else if(from.equals(getUnitFrom("oz")) && to.equals(getUnitTo("kg"))){
        rate = 0.028;
    }
    else if(from.equals(getUnitFrom("lb")) && to.equals(getUnitTo("g"))){
        rate = 453.6;
    }
    else if(from.equals(getUnitFrom("lb")) && to.equals(getUnitTo("kg"))){
        rate = 0.045;
    }

    if(from.equals(getUnitFrom("in")) && to.equals(getUnitTo("mm"))){
        rate = 25.4;
    }
    else if(from.equals(getUnitFrom("in")) && to.equals(getUnitTo("cm"))){
        rate = 2.54;
    }
    else if(from.equals(getUnitFrom("in")) && to.equals(getUnitTo("m"))){
        rate = 0.0254;
    }
    else if(from.equals(getUnitFrom("ft")) && to.equals(getUnitTo("mm"))){
        rate = 304.8;
    }
    else if(from.equals(getUnitFrom("ft")) && to.equals(getUnitFrom("cm"))){
        rate = 30.48;
    }
    else if(from.equals(getUnitFrom("ft")) && to.equals(getUnitFrom("m"))){
        rate = 0.3048;
    }

    return rate;
}

public static void main(String[] args) {
    String convertFrom = getUnitFrom();
    String convertTo = getUnitTo();
    double valueOf = getValue();
    System.out.println(getValue() + " " + getUnitFrom() + " = " + (getValue() * getConversionRate()) + " " + getUnitTo());

}
public static Scanner input = new Scanner(System.in);

```