Javapoet: Generate method definitions with some configurations

In this post, I am going to explain how to generate method definitions with some configuration.

 

Example

private static MethodSpec dynamicMethod(String name, int startingNumber, int endingNumber, char operator) {    
  return MethodSpec.methodBuilder(name)
          .returns(int.class)
          .addStatement("int result = 0")
          .beginControlFlow("for (int i = " + startingNumber + "; i <= " + endingNumber + "; i++)")
          .addStatement("result = result " + operator + " i")
          .endControlFlow().addStatement("return result")
      .build();
}

 

dynamicMethod("addFrom10To20", 10, 20, '+');

Above definition generates below code snippet.

int addFrom10To20() {
    int result = 0;
    for (int i = 10; i <= 20; i++) {
      result = result + i;
    }
    return result;
  }

 

dynamicMethod("addFrom0To30", 10, 30, '+');

Above snippet generates below code snippet.

int addFrom0To30() {
  int result = 0;
  for (int i = 10; i <= 20; i++) {
    result = result + i;
  }
  return result;
}

 

Find the below working application.

 

MethodDefinitionWithSomeConfig.java

package com.sample.app;
import java.io.IOException;

import javax.lang.model.element.Modifier;

import com.squareup.javapoet.JavaFile;
import com.squareup.javapoet.MethodSpec;
import com.squareup.javapoet.TypeSpec;

public class MethodDefinitionWithSomeConfig {
  
  private static MethodSpec dynamicMethod(String name, int startingNumber, int endingNumber, char operator) {    
    return MethodSpec.methodBuilder(name)
            .returns(int.class)
            .addStatement("int result = 0")
            .beginControlFlow("for (int i = " + startingNumber + "; i <= " + endingNumber + "; i++)")
            .addStatement("result = result " + operator + " i")
            .endControlFlow().addStatement("return result")
        .build();
  }
  
  public static void main(String args[]) throws IOException {
    MethodSpec addFrom10To20 = dynamicMethod("addFrom10To20", 10, 20, '+');
    MethodSpec addFrist30Numbers = dynamicMethod("addFrom0To30", 0, 30, '+');
    
    String className = "HelloWorld";
    TypeSpec.Builder classBuilder = TypeSpec.classBuilder(className);
    classBuilder.addModifiers(Modifier.PUBLIC, Modifier.FINAL);
    classBuilder.addMethod(addFrom10To20);
    classBuilder.addMethod(addFrist30Numbers);
    TypeSpec helloWorldTypeSpec = classBuilder.build();

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

    javaFile.writeTo(System.out);
  }

}

 

Generated code

package com.sample.app;

public final class HelloWorld {
  int addFrom10To20() {
    int result = 0;
    for (int i = 10; i <= 20; i++) {
      result = result + i;
    }
    return result;
  }

  int addFrom0To30() {
    int result = 0;
    for (int i = 0; i <= 30; i++) {
      result = result + i;
    }
    return result;
  }
}

 

 

 

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