Java constructor (anti-pattern) super-classing String -


the intention of following design allow string values (in effect) subclassed enable number of conflicting constructor methods established (e.g. method signatures same though parameter names different).

kindly consider following (non-functional) design:

id interface (an empty - marker interface)

public interface id {}

classes interface (an empty - marker interface)

public interface classes {}

title interface (an empty - marker interface)

public interface title {}

tool class

public tool(id id) throws exception {     this.span = new span();      this.span.addattribute(new attribute(attribute.id, (string)((object) id))); }  public tool(classes classes) throws exception {     this.span = new span();     this.span.addattribute(new attribute(attribute.class, (string)((object) classes))); }  public tool(title title) throws exception {     this.span = new span();     this.span.addattribute(new attribute(attribute.title, (string)((object) title))); }  public tool(id id, classes classes, title title) throws exception {     this.span = new span();     this.span.addattribute(new attribute(attribute.id, (string)((object) id)));     this.span.addattribute(new attribute(attribute.class, (string)((object) classes)));     this.span.addattribute(new attribute(attribute.title, (string)((object) title))); }  public void test() throws exception {     tool hammer = new tool((id)((object)"hammer"));     tool poweredtool = new tool((classes)((object)"tool powered"));     tool tool = new tool((id)((object)"invention"), (classes)((object)"tool powered"), (title)((object)"define new tool")); }

the approach requires interface per parameter "type" , down cast / cast specific interface "type" object , string...

i uncomfortable approach , i'm hoping there's design pattern out there alleviate desire subclass string (solely purpose of constructor method differentiation)...

i have variadic method takes arbitrary collection of name value pairs provide alternative fixed parameter constructors, constructors shown above common combinations , therefore convenience programmer presently being contemplated being provided...

thanks!

considering how constructors suggest rid of them , use builder pattern instead:

class tool {      private tool() { // preventing direct instantiation private constructor         this.span = new span();     }      ... // tool class code      public static builder builder() {         return new builder();     }      public static class builder {         private final tool tool = new tool();          public builder withid(string id) {              tool.span.addattribute(new attribute(attribute.id, id));             return this;         }             ... // other methods in same manner          public tool build() {             // add validation if necessary             return tool;         }     } }

usage:

tool tool = tool.builder()                 .withid("id")                 .withclasses("classa, classb")                 .build();

-

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