how to generate symbol Class<?> with javapoet

Question

i want to generate a field like this:

public static Map> ID_MAP = new HashMap>();

Answer 1

Using ParameterizedTypeName.get() worked for me -

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

    TypeName wildcard = WildcardTypeName.subtypeOf(Object.class);

    TypeName classOfAny = ParameterizedTypeName.get(
            ClassName.get(Class.class), wildcard);

    TypeName string = ClassName.get(String.class);

    TypeName mapOfStringAndClassOfAny = ParameterizedTypeName.get(ClassName.get(Map.class), string, classOfAny);

    TypeName hashMapOfStringAndClassOfAny = ParameterizedTypeName.get(ClassName.get(HashMap.class), string, classOfAny);

    FieldSpec fieldSpec = FieldSpec.builder(mapOfStringAndClassOfAny, "ID_MAP")
            .addModifiers(Modifier.PUBLIC, Modifier.STATIC)
            .initializer("new $T()", hashMapOfStringAndClassOfAny)
            .build();

    TypeSpec fieldImpl = TypeSpec.classBuilder("FieldImpl")
            .addModifiers(Modifier.PUBLIC, Modifier.FINAL)
            .addField(fieldSpec)
            .build();

    JavaFile javaFile = JavaFile.builder("com", fieldImpl)
            .build();

    javaFile.writeTo(System.out);
}

---

Imports used by me -

import com.squareup.javapoet.*;
import javax.lang.model.element.Modifier;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

---

This generates the output as -

package com;

import java.lang.Class;
import java.lang.String;
import java.util.HashMap;
import java.util.Map;

public final class FieldImpl {
  public static Map> ID_MAP = new HashMap>();
}