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import java.lang.reflect.Method; import java.util.HashMap; import java.util.Map; public class Base { // The fromJSON method that parses the JSON and sets the values public void fromJSON(String json) { try { // Manually parse the JSON string into a map of field names and values Map<String, String> fields = parseJSON(json); // Iterate through the fields and find matching setters using reflection for (Map.Entry<String, String> entry : fields.entrySet()) { String fieldName = entry.getKey(); String fieldValue = entry.getValue(); // Find the setter method corresponding to this field String setterMethodName = "set" + capitalize(fieldName); Method setterMethod = findSetterMethod(setterMethodName, fieldValue); if (setterMethod != null) { // Invoke the setter method with the appropriate value invokeSetter(setterMethod, fieldValue); } } } catch (Exception e) { e.printStackTrace(); } } // Manually parse the JSON string into a Map<String, String> private Map<String, String> parseJSON(String json) { Map<String, String> fields = new HashMap<>(); // Remove surrounding curly braces and trim the string json = json.trim().substring(1, json.length() - 1).trim(); // Split the JSON string into key-value pairs String[] keyValuePairs = json.split(",\\s*"); // Loop through the pairs and extract key-value for (String pair : keyValuePairs) { String[] keyValue = pair.split(":\\s*"); String key = keyValue[0].trim().replaceAll("\"", ""); // Remove quotes around key String value = keyValue[1].trim().replaceAll("\"", ""); // Remove quotes around value // Handle values without quotes as well (like numbers or booleans) fields.put(key, value); } return fields; } // Capitalizes the first letter of a string (helper method for setter name matching) private String capitalize(String fieldName) { return fieldName.substring(0, 1).toUpperCase() + fieldName.substring(1); } // Find a matching setter method using reflection private Method findSetterMethod(String setterMethodName, String fieldValue) { try { // Check for setter methods in the current class for (Method method : this.getClass().getMethods()) { if (method.getName().equals(setterMethodName)) { if (method.getParameterCount() == 1) { // Match based on the parameter type Class<?> paramType = method.getParameterTypes()[0]; if (paramType.equals(String.class)) { return method; } else if (paramType.equals(int.class) && isInteger(fieldValue)) { return method; } else if (paramType.equals(double.class) && isDouble(fieldValue)) { return method; } else if (paramType.equals(boolean.class) && isBoolean(fieldValue)) { return method; } } } } } catch (Exception e) { e.printStackTrace(); } return null; } // Invokes the setter method dynamically using reflection private void invokeSetter(Method setterMethod, String fieldValue) { try { Class<?> paramType = setterMethod.getParameterTypes()[0]; if (paramType.equals(String.class)) { setterMethod.invoke(this, fieldValue); } else if (paramType.equals(int.class)) { setterMethod.invoke(this, Integer.parseInt(fieldValue)); } else if (paramType.equals(double.class)) { setterMethod.invoke(this, Double.parseDouble(fieldValue)); } else if (paramType.equals(boolean.class)) { setterMethod.invoke(this, Boolean.parseBoolean(fieldValue)); } } catch (Exception e) { e.printStackTrace(); } } // Helper method to check if a string represents an integer private boolean isInteger(String value) { try { Integer.parseInt(value); return true; } catch (NumberFormatException e) { return false; } } // Helper method to check if a string represents a double private boolean isDouble(String value) { try { Double.parseDouble(value); return true; } catch (NumberFormatException e) { return false; } } // Helper method to check if a string represents a boolean private boolean isBoolean(String value) { return value.equalsIgnoreCase("true") || value.equalsIgnoreCase("false"); } } class Person extends Base { private String name; private int age; // Getter and Setter methods public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } @Override public String toString() { return "Person{name='" + name + "', age=" + age + "}"; } } public class Main { public static void main(String[] args) { String json = "{\"Name\": \"John\", \"Age\": 33}"; Person person = new Person(); person.fromJSON(json); System.out.println(person); // Output: Person{name='John', age=33} // Another example with booleans and doubles String json2 = "{\"Name\": \"Alice\", \"Age\": 28, \"IsEmployed\": true, \"Salary\": 55000.50}"; Person person2 = new Person(); person2.fromJSON(json2); System.out.println(person2); // Output: Person{name='Alice', age=28} } }
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