Java - ObjectStreamClass lookupAny(Class<?> cl) method

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Description

The Java ObjectStreamClass lookupAny(Class<?> cl) method returns the descriptor for any class, regardless of whether it implements Serializable.

• lookupAny() is similar to lookup(), but it works for any class, not just serializable ones.

• It returns an ObjectStreamClass instance, even if the class does not implement Serializable.

• It's useful when −

  • You need to inspect fields or class metadata regardless of serializability.

  • You're building custom serialization tools or class inspectors.

lookup() returns null for non-serializable classes. lookupAny() never returns null.

Declaration

Following is the declaration for java.io.ObjectStreamClass.lookupAny(Class<?> cl) method.

public static ObjectStreamClass lookupAny(Class<?> cl)

Parameters

cl − class for which to get the descriptor.

Return Value

This method returns the class descriptor for the specified class.

Exception

NA

Example - Usage of ObjectStreamClass lookupAny(Class<?> cl) method

The following example shows the usage of ObjectStreamClass lookupAny(Class<?> cl) method.

ObjectStreamClassDemo.java

package com.tutorialspoint;

import java.io.ObjectStreamClass;

public class ObjectStreamClassDemo {
   public static void main(String[] args) {

      // create a new object stream class for Integers
      ObjectStreamClass osc = ObjectStreamClass.lookupAny(Integer.class);

      // get the name for Integers
      System.out.println("" + osc.getName());

      // create a new object stream class for Thread, which is not serializable
      ObjectStreamClass osc2 = ObjectStreamClass.lookupAny(Thread.class);

      // get the name for Calendar
      System.out.println("" + osc2.getName());
   }
}

Output

Let us compile and run the above program, this will produce the following result −

java.lang.Integer
java.util.Calendar

Example - Lookup a non-serializable class and print its name

The following example shows the usage of ObjectStreamClass lookupAny(Class<?> cl) method. We're using lookupAny() to inspect a class that is not serializable.

ObjectStreamClassDemo.java

package com.tutorialspoint;

import java.io.ObjectStreamClass;
import java.io.Serializable;

public class ObjectStreamClassDemo {
   public static void main(String[] args) {
      ObjectStreamClass osc = ObjectStreamClass.lookupAny(Settings.class);

      System.out.println("Class: " + osc.getName());
      System.out.println("Is class serializable? " + Serializable.class.isAssignableFrom(osc.forClass()));
   }

   static class Settings {
      String theme;
      boolean darkMode;
   }
}

Output

Let us compile and run the above program, this will produce the following result−

Class: com.tutorialspoint.ObjectStreamClassDemo$Settings
Is class serializable? false

Explanation

• Settings does not implement Serializable, but lookupAny() still returns metadata.

• We use forClass() and isAssignableFrom() to check if it's serializable.

Example - Compare lookup() and lookupAny() behavior

The following example shows the usage of ObjectStreamClass lookupAny(Class<?> cl) method. We're showcasing how lookup() returns null while lookupAny() still works.

ObjectStreamClassDemo.java

package com.tutorialspoint;

import java.io.ObjectStreamClass;

public class ObjectStreamClassDemo {
   public static void main(String[] args) {
      ObjectStreamClass normal = ObjectStreamClass.lookup(Helper.class);
      ObjectStreamClass any = ObjectStreamClass.lookupAny(Helper.class);

      System.out.println("lookup() result: " + (normal == null ? "null" : "found"));
      System.out.println("lookupAny() result: " + any.getName());
   }

   static class Helper {
      int version;
      String type;
   }
}

Output

Let us compile and run the above program, this will produce the following result−

lookup() result: null
lookupAny() result: com.tutorialspoint.ObjectStreamClassDemo$Helper

Explanation

• lookup() returns null because Helper is not serializable.

• lookupAny() still returns a valid ObjectStreamClass.