JAVA_Object类equals()方法

equals

public boolean equals(Object obj)

Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

    It is reflexive: for any non-null reference value x, x.equals(x) should return true.
    It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
    It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true,
  then x.equals(z) should return true.
    It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently
  return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
    For any non-null reference value x, x.equals(null) should return false.

The equals method for class Object implements the most discriminating possible equivalence relation on objects;that is,
for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

Note that it is generally necessary to override the hashCode method whenever this method is overridden,
so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

Parameters:
    obj - the reference object with which to compare.
Returns:
    true if this object is the same as the obj argument; false otherwise.
See Also:
    hashCode(), HashMap

equals

public boolean equals(Object anObject)

Compares this string to the specified object. 
The result is true if and only if the argument is not null and is a String object that represents the same sequence of characters as this object.

Overrides:
    equals in class Object
Parameters:
    anObject - The object to compare this String against
Returns:
    true if the given object represents a String equivalent to this string, false otherwise
See Also:
    compareTo(String), equalsIgnoreCase(String)