For example I have two simple as possible classes, A and B I want to take some action on objects of B, if some specific field of A object is changed I should do one thing, If some other field is changed I should do second thing, how can I do that with Lambda?
A:
public class A {
private int someField;
private String nextField;
public A(int someField, String nextField) {
this.someField = someField;
this.nextField = nextField;
}
public int getSomeField() {
return someField;
}
public void setSomeField(int someField) {
this.someField = someField;
}
public String getNextField() {
return nextField;
}
public void setNextField(String nextField) {
this.nextField = nextField;
}
}
B:
public class B {
private String someField;
public String getSomeField() {
return someField;
}
public void setSomeField(String someField) {
this.someField = someField;
}
public B(String someField) {
this.someField = someField;
}
}
Demo:
public class Demo {
public static <T> boolean isFieldChanged(T oldValue, T newValue) {
return !Objects.equals(oldValue, newValue);
}
public static void someActionOne(B test){
return;
}
public static void someActionTwo(B test){
return;
}
public static void main(String[] args) {
A oldData = new A(35, "old");
A clientData = new A(25, "ClientData");
Consumer<B> action = null;
if (isFieldChanged(oldData.getNextField(), clientData.getNextField())) {
action = Demo::someActionOne;
} else if (isFieldChanged(oldData.getSomeField(), clientData.getSomeField())) {
action = Demo::someActionTwo;
}
List<B> mockData = new ArrayList<>(Arrays.asList(new B("test1"), new B("test2")));
mockData.forEach(b -> action.accept(b));
}
}
How can I avoid compile error in that case?
To be effectively-final, a variable must not be changed after initialization.
If you want to use different actions, just initialize them twice:
public static void main(String[] args) {
A oldData = new A(35, "old");
A clientData = new A(25, "ClientData");
List<B> mockData = new ArrayList<>(Arrays.asList(new B("test1"), new B("test2")));
if (isFieldChanged(oldData.getNextField(), clientData.getNextField())) {
mockData.forEach(Demo::someActionOne);
} else if (isFieldChanged(oldData.getSomeField(), clientData.getSomeField())) {
mockData.forEach(Demo::someActionTwo);
}
}