Using Reflection to Count Methods.

Question

I have to write a function

public static int[] countGettersandSetters (String classname)

to count the number of get and set methods and return as an array where index 0 are sets and index 1 are gets.

Can anyone give me a high level approach to how to solve this problem?

Use Java Reflection - docs.oracle.com/javase/tutorial/reflect — Greg Kopff
– Greg Kopff, Commented Aug 5, 2013 at 3:14

Ravi K Thapliyal · Accepted Answer · 2013-08-05 03:41:35Z

10

public static int[] countGettersandSetters (String className)
    int[] count = new int[2];
    Method[] methods = Class.forName(className).getDeclaredMethods();
    for (Method method : methods) {
        if (method.getName().startsWith("set")) {
            count[0]++;
        } else if (method.getName().startsWith("get") ||
                   method.getName().startsWith("is")) { // to incl. boolean properties
            count[1]++;
        } 
    }
    return count;
}

For a concise tutorial on Reflection API take a look here.

edited Aug 5, 2013 at 3:41

answered Aug 5, 2013 at 3:24

Ravi K Thapliyal

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5 Comments

MadProgrammer Over a year ago

I could be wrong, haven't tested it, but I believe this will only return the methods for the current class and not any declared by it's parent classes...

Ravi K Thapliyal Over a year ago

@MadProgrammer, that's correct. getDeclaredMethods() excludes inherited methods.

Ravi K Thapliyal Over a year ago

@DownVoter, The idea is to give OP a push in the right direction. Not churn out production class code.

BlackJoker Over a year ago

the setter must have exactly 1 parameter and the getter should not has any parameter.and your answer didn't consider that.

Ravi K Thapliyal Over a year ago

@J.Rush, Please, note that the methods are not being invoked here. So, how many arguments they take is immaterial. And, the other answers here that check for field names as well are incorrect because JavaBean properties do not require the underlying field names to match with their getters/setters.

ChanceLai · Accepted Answer · 2013-08-05 03:52:25Z

1

public static int[] countGettersandSetters(String c) throws ClassNotFoundException {
    int[] count = new int[2];
    Class<?> classs = Class.forName(c);
    Field[] fields = classs.getDeclaredFields();
    for (Field field : fields) {
        String name = field.getName();
        try {
            classs.getMethod("set"+name.substring(0, 1).toUpperCase()+name.substring(1) , null);
            count[0]++;
        } catch (NoSuchMethodException e) {
        }
        try {
            classs.getMethod("get"+name.substring(0, 1).toUpperCase()+name.substring(1), field.getType());
            count[1]++;
        } catch (NoSuchMethodException e) {
        }
    }
    return count;
}

answered Aug 5, 2013 at 3:52

ChanceLai

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1 Comment

Ravi K Thapliyal Over a year ago

JavaBean properties do not require the underlying field names to match their getters/setters. So, the check is unnecessary and may potentially report an incorrect number of property methods.

s.d · Accepted Answer · 2013-08-05 03:33:24Z

0

Considering the standard naming convention, check that there exists a method with "get" or "set" prefixed to the name of a field of the class:

public static int[] count(Class<? extends Object> c) {
    int[] counts = new int[2];

    Field[] fields = c.getDeclaredFields();
    Method[] methods = c.getDeclaredMethods();

    Set<String> fieldNames = new HashSet<String>();
    List<String> methodNames = new ArrayList<String>();

    for (Field f : fields){
        fieldNames.add(f.getName().toLowerCase());
    }

    for (Method m : methods){
        methodNames.add(m.getName().toLowerCase());
    }

    for (String name : methodNames){
        if(name.startsWith("get") && fieldNames.contains(name.substring(3))){
            counts[0]++;
        }else if(name.startsWith("set") && fieldNames.contains(name.substring(3))){
            counts[1]++;
        }
    }

    return counts;
}

If you want to get all inherited getters/setters as well, replace getDeclaredFields() and getDeclaredMethods() with getFields() and getMethods().

answered Aug 5, 2013 at 3:33

s.d

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1 Comment

Ravi K Thapliyal Over a year ago

JavaBean properties do not require the underlying field names to match their getters/setters. So, the check is unnecessary and may potentially report an incorrect number of property methods.

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