Example

public class ClassA {
private File f;
private File f2;
public void methodA {

f.rename(f2);
//...
}

}
Solution
Store the method invocation's return value.

public class ClassA {
private File f;
private File f2;
public void methodA {

int i=f.rename(f2);
// Use the value of i in some way...
}

}