从HashMap获取方法get（）返回

Question

I am currently working in Processing 3, and am having troubles understanding the return of a HashMap. I have a map, Map<String, Chromosome> genes = new HashMap<String, Chromosome>() which uses my classes,

class Chromosome{
  Genotype geneOne;
  Genotype geneTwo;

  Chromosome(){ ... }

  Chromosome(Genotype gOne, Genotype gTwo){ ... }

  void setGeneOne(Genotype gene){ ... }

  void setGeneTwo(Genotype gene){ ... }

  Genotype getDomGene(){ ... }

  Genotype getRecGene(){ ... }
}

class Genotype{
  Object value;
  float weight;

  public Genotype(int value, float weight){ ... }

  public Genotype(int[] value, float weight){ ... }

  public Genotype(String value, float weight){ ... }

  public Genotype(float value, float weight){ ... }

  public Object getValue(){ ... }

  public float getWeight(){ ... }

  public void setValue(int value){ ... }

  public void setValue(int[] value){ ... }

  public void setValue(String value){ ... }

  public void setValue(float value){ ... }
}

What I'm thinking is that when I "get" a value from the map, I should be able to access its methods from there. IE

class Flower{
    Map<String, Chromosome> genes;
    Flower(){
        genes = new HashMap<String, Chromosome>();
        genes.put("color", new Chromosome(new Genotype(64, 1.0), new Genotype(25,0.5)));
        Genotype test = genes.get("color").getDomGene(); //should return the first param passed to the new chromosome
    }
}

I'm hoping to avoid having to declare the returned object every time I use it. From all of 20 minutes of googling, I can't seem to find anything about this working, so why does this not work, and what can be done to work around it?

Answer 1

You should just return genOne in getDomGene method.

Chromosome class.

package gen;

class Chromosome {

    Genotype geneOne;
    Genotype geneTwo;

    Chromosome() {
        System.out.println("Chromosome.Chromosome");
    }

    Chromosome(Genotype gOne, Genotype gTwo) {
        System.out.println("Chromosome.Chromosome");
    }

    void setGeneOne(Genotype gene) {
        System.out.println("Chromosome.setGeneOne");
    }

    void setGeneTwo(Genotype gene) {
        System.out.println("Chromosome.setGeneTwo");
    }

    Genotype getDomGene() {
        System.out.println("return genOne");
        return geneOne;
    }

    Genotype getRecGene() {
        System.out.println("return genTwo");
        return geneTwo;
    }
}

Genotype class

package gen;

class Genotype {

    Object value;
    float weight;

    public Genotype(int value, float weight) {
        System.out.println("Genotype.Genotype");
    }

    public Genotype(int[] value, float weight) {
        System.out.println("Genotype.Genotype");
    }

    public Genotype(String value, float weight) {
        System.out.println("Genotype.Genotype");
    }

    public Genotype(float value, float weight) {
        System.out.println("Genotype.Genotype");
    }

    public Object getValue() {
        System.out.println("Genotype.getValue");
        return null;
    }

    public void setValue(String value) {
        System.out.println("Genotype.setValue");
    }

    public void setValue(float value) {
        System.out.println("Genotype.setValue");
    }

    public void setValue(int value) {
        System.out.println("Genotype.setValue");
    }

    public void setValue(int[] value) {
        System.out.println("Genotype.setValue");
    }

    public float getWeight() {
        System.out.println("Genotype.getWeight");
        return 0;
    }
}

Flower class.

package gen;

import java.util.HashMap;
import java.util.Map;

class Flower {

    Map<String, Chromosome> genes;

    Flower() {
        genes = new HashMap<>();
        genes.put("color", new Chromosome(new Genotype(64, 1.0f), new
                Genotype(25, 0.5f)));
        Genotype test = genes.get("color")
                .getDomGene(); //should return the first param passed to the new chromosome
    }

    public static void main(String[] args) {
        new Flower();
    }
}

It prints

Genotype.Genotype
Genotype.Genotype
Chromosome.Chromosome
return genOne

return genOne means that you have an access to the geneOne field of Chromosome class, that is its first parameter.

Answer 2

if you put class Flower in a different package? you can't see methods that are not "public". try putting all classes in the same package or make the method public

public Genotype getDomGene(){ ... }

public Genotype getRecGene(){ ... }