CODEWITHSUNDEEP
java
Rakib
Rakib

Reputation: 2086

Java Reflection: Difference between getMethods() and getDeclaredMethods()

Can someone please elaborate on this, and explain the difference between the two methods, and when/why you would want to use one over the others

Upvotes: 80

Views: 36957

Answers (2)

Ian Boyd
Ian Boyd

Reputation: 256671

Short Version

Method Public Non-public Inherited
getMethods() ✔️ ❌ ✔️
getDeclaredMethods() ✔️ ✔️ ❌

Long version

Methods getMethods() getDeclaredMethods
public ✔️ ✔️
protected ❌ ✔️
private ❌ ✔️
static public ✔️ ✔️
static protected ❌ ✔️
static private ❌ ✔️
default public ✔️ ✔️
default protected ❌ ✔️
default private ❌ ✔️
inherited public ✔️ ❌
inherited protected ❌ ❌
inherited private ❌ ❌
inherited static private ✔️ ❌
inherited static protected ❌ ❌
inherited static private ❌ ❌
default inherited public ✔️ ❌
default inherited protected ❌ ❌
default inherited private ❌ ❌

If your goal, like mine, was to get public methods of a class:

Method Public Non-public Inherited
getMethods() ✔️ ❌ ✔️
getDeclaredMethods() ✔️ ✔️ ❌
getPublicMethods() ✔️ ❌ ❌

and nothing else:

Methods getPublicMethods()
public ✔️
protected ❌
private ❌
static public ❌
static protected ❌
static private ❌
default public ❌
default protected ❌
default private ❌
inherited public ❌
inherited protected ❌
inherited private ❌
inherited static private ❌
inherited static protected ❌
inherited static private ❌
default inherited public ❌
default inherited protected ❌
default inherited private ❌

You have to do it yourself:

Iterable<Method> getPublicMethods(Object o) {
   List<Method> publicMethods = new ArrayList<>();

   // getDeclaredMethods only includes methods in the class (good)
   // but also includes protected and private methods (bad)
   for (Method method : o.getClass().getDeclaredMethods()) {
      if (!Modifier.isPublic(method.getModifiers())) continue; //only **public** methods
      if (!Modifier.isStatic(method.getModifiers())) continue; //only public **methods**
      publicMethods.add(method);
   }
   return publicMethods;
}

Upvotes: 25

Thilo
Thilo

Reputation: 262494

getDeclaredMethods includes all methods declared by the class itself, whereas getMethods returns only public methods, but also those inherited from a base class (here from java.lang.Object).

Read more about it in the Javadocs for getDeclaredMethod and getMethods.

Upvotes: 110

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