Implementations detect changes between two different task outputs in relation to the used data of them.
This interface is used to determine during incremental builds if a task needs to be rerun based on its input tasks.
If a task A depends on task B and a change detector was specified previously, then it will be invoked to detect any changes between different outputs of the input task B.
Tasks which have their input tasks' outputs changed will be rerun in case of incremental builds.
This interface can be used to partially depend on tasks which can significantly improve build performance.
Task A depends on task B.
Task B returns a complex output with fields named X and Y.
Task A only utilizes the value of the field Y to properly execute. In this case task A can specify a change detector which compares the expected Y value to the current one specified by the isChanged(
If task B is rerun, and the field Y does not change, then task A will not be rerun, as its input task B is not considered to be changed in relation to task A.
equals method implements an equivalence relation on non-null object references:
- It is reflexive: for any non-null reference value
- It is symmetric: for any non-null reference values
trueif and only if
- It is transitive: for any non-null reference values
- It is consistent: for any non-null reference values
y, multiple invocations of
trueor consistently return
false, provided no information used in
equalscomparisons on the objects is modified.
- For any non-null reference value
equals method for class
Object implements the most discriminating possible equivalence
relation on objects; that is, for any non-null reference values
y, this method returns
true if and only if
y refer to the same object (
x == y has the value
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.
trueif this object is the same as the obj argument;
The general contract of
- Whenever it is invoked on the same object more than once during an execution of a Java application, the
hashCodemethod must consistently return the same integer, provided no information used in
equalscomparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
- If two objects are equal according to the
equals(Object)method, then calling the
hashCodemethod on each of the two objects must produce the same integer result.
- It is not required that if two objects are unequal according to the
Object)method, then calling the
hashCodemethod on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.
As much as is reasonably practical, the hashCode method defined by class
Object does return distinct
integers for distinct objects. (This is typically implemented by converting the internal address of the object
into an integer, but this implementation technique is not required by the Java™ programming language.)
If this methods throws a RuntimeException then it is an implementation error, however the caller can
interpret it as if it returned
trueif it is considered to be changed.