Adapter Pattern

ComplexNumber.java

package com.example.adapter;

public interface ComplexNumber {
  
  double real();
  
  double imaginary();
}

ComplexNumberAdapter.java

package com.example.adapter;

public ComplexNumberAdapter implements ComplexNumber {

  private final RealNumber realNumber;

  public ComplexNumberAdapter(RealNumber realNumber) {
    this.realNumber = realNumber;
  }
  
  @Override
  public double real() {
    return realNumber.value();
  }
  
  @Override
  public double imaginary() {
    return 0;
  }

}

RealNumber.java

package com.example.adapter;

public interface RealNumber {
  double value();
}

public final class Pi implements RealNumber {
  
  @Override
  public double value() {
    return 3.14159;
  }
}