Javapoet: Add generic parameters to a method

Using ‘TypeVariableName’ you can define generic types.

 

Example

TypeVariableName typeVariableName = TypeVariableName.get("T");

Find the below working application.

 

AddGenericParameterToAMethod.java

package com.sample.app;

import java.io.IOException;

import javax.lang.model.element.Modifier;

import com.squareup.javapoet.FieldSpec;
import com.squareup.javapoet.JavaFile;
import com.squareup.javapoet.MethodSpec;
import com.squareup.javapoet.ParameterSpec;
import com.squareup.javapoet.TypeSpec;
import com.squareup.javapoet.TypeVariableName;

public class AddGenericParameterToAMethod {
	public static void main(String args[]) throws IOException {

		ParameterSpec empName = ParameterSpec.builder(String.class, "name").addModifiers(Modifier.FINAL).build();

		TypeVariableName typeVariableName = TypeVariableName.get("T");
		FieldSpec idField = FieldSpec.builder(typeVariableName, "id").build();

		MethodSpec constructor = MethodSpec.methodBuilder("getDetails").returns(String.class)
				.addModifiers(Modifier.PUBLIC).addParameter(typeVariableName, "id").addParameter(empName)
				.addStatement("return $S", "Hi").build();

		FieldSpec nameField = FieldSpec.builder(String.class, "name").build();
		TypeSpec helloWorldTypeSpec = TypeSpec.classBuilder("Employee").addTypeVariable(typeVariableName)
				.addModifiers(Modifier.PUBLIC, Modifier.FINAL).addMethod(constructor).addField(nameField)
				.addField(idField).build();

		String packageName = "com.sample.app";
		JavaFile javaFile = JavaFile.builder(packageName, helloWorldTypeSpec).build();

		javaFile.writeTo(System.out);
	}

}

Generated Code

package com.sample.app;

import java.lang.String;

public final class Employee<T> {
  String name;

  T id;

  public String getDetails(T id, final String name) {
    return "Hi";
  }
}

 

 

Previous                                                    Next                                                    Home