Pass By Value
Parameters are like local variables in that their scope is limited to the method's curly braces { }.
* The difference is that a parameter will always be initialized with data from a caller.
When a caller calls a method, Java copies the caller's data into method's parameter. * This is known as pass-by-value.
pass-by-value¶
Copying data from a method argument into a method parameter.
This means the caller's variable and method's parameter are not linked, so assigning a new value to the parameter will not change the caller's variable.
Think of the parameter as a local variable with a copy of the caller's data.
Drill¶
Methods/src/drills/PassByValue.java
Complete the drill according to the instructions. Note that the local variable x in main can have the same name, x, as the changeIt method parameter. This is because they are each "local to" their respective methods.
Practice Exercise¶
"Is Java pass-by-value or pass-by-reference?" is a common interview question.
Java is pass-by-value because data is copied from the caller to the method parameters, so assigning a different value to a parameter will not change a caller's variable.
In pass-by-reference programming languages, assigning new data to a method parameter could change the caller's variable.