com.google.common.base
Class Objects

java.lang.Object
  com.google.common.base.Objects

@GwtCompatible
public final class Objects
extends Object

Helper functions that can operate on any Object.

Since:

2 (imported from Google Collections Library)

Author:

Laurence Gonsalves

equal

public static boolean equal(@Nullable
                            Object a,
                            @Nullable
                            Object b)

Determines whether two possibly-null objects are equal. Returns:

• true if a and b are both null.
• true if a and b are both non-null and they are equal according to Object.equals(Object).
• false in all other situations.

This assumes that any non-null objects passed to this function conform to the equals() contract.

hashCode

public static int hashCode(Object... objects)

Generates a hash code for multiple values. The hash code is generated by calling Arrays.hashCode(Object[]).

This is useful for implementing Object.hashCode(). For example, in an object that has three properties, x, y, and z, one could write:

 public int hashCode() {
   return Objects.hashCode(getX(), getY(), getZ());
 }

Warning: When a single object is supplied, the returned hash code does not equal the hash code of that object.

toStringHelper

public static Objects.ToStringHelper toStringHelper(Object self)

Creates an instance of Objects.ToStringHelper.

This is helpful for implementing Object.toString(). For example, in an object that contains two member variables, x, and y, one could write:

   
   public class ClassName {
     public String toString() {
       return Objects.toStringHelper(this)
           .add("x", x)
           .add("y", y)
           .toString();
     }
   }
 

Assuming the values of x and y are 1 and 2, this code snippet returns the string "ClassName{x=1, y=2}".

Parameters:

self - the object to generate the string for (typically this), used only for its class name

Since:

2

toStringHelper

public static Objects.ToStringHelper toStringHelper(Class<?> clazz)

Creates an instance of Objects.ToStringHelper in the same manner as toStringHelper(Object), but using the name of clazz instead of using an instance's Object.getClass().

Parameters:

clazz - the Class of the instance

Since:

7 (source-compatible since 2)

toStringHelper

public static Objects.ToStringHelper toStringHelper(String className)

Creates an instance of Objects.ToStringHelper in the same manner as toStringHelper(Object), but using className instead of using an instance's Object.getClass().

Parameters:

className - the name of the instance type

Since:

7 (source-compatible since 2)

firstNonNull

public static <T> T firstNonNull(@Nullable
                                 T first,
                                 @Nullable
                                 T second)

Returns the first of two given parameters that is not null, if either is, or otherwise throws a NullPointerException.

Returns:

first if first is not null, or second if first is null and second is not null

Throws:

NullPointerException - if both first and second were null

Since:

3