The problem I am trying to solve is described in OO: dependent class needs information from grandparent class
import java.util.function.Supplier;
public class SupplyMe {
private Supplier<String> supplied;
public SupplyMe(Supplier<String> supplied) {
this.supplied = supplied;
}
public void printSupplied() {
System.out.println(supplied.get());
}
public static void main(String[] args) {
String changingStr = "hi";
Supplier<String> helloStrSupplier = () -> changingStr;
SupplyMe mySupplyMe = new SupplyMe(helloStrSupplier);
mySupplyMe.printSupplied();
changingStr = "hi2";
mySupplyMe.printSupplied();
}
}
the following code is throwing
SupplyMe.java:18: error: local variables referenced from a lambda expression must be final or effectively final
Supplier<String> helloStrSupplier = () -> changingStr;
What can I do to make Supplier be able to supple the value at runtime?
i was able to get it work by doing this
import java.util.function.Supplier;
public class SupplyMe {
public static String changingStr = "";
private Supplier<String> supplied;
public SupplyMe(Supplier<String> supplied) {
this.supplied = supplied;
}
public void printSupplied() {
System.out.println(supplied.get());
}
public static void main(String[] args) {
changingStr = "hi";
//Supplier<String> helloStrSupplier = changingStr;
Supplier<String> helloStrSupplier = new DynamicSupplier();
SupplyMe mySupplyMe = new SupplyMe(helloStrSupplier);
mySupplyMe.printSupplied();
changingStr = "hi2";
mySupplyMe.printSupplied();
}
static class DynamicSupplier implements Supplier<String> {
#Override
public String get() {
return changingStr;
}
}
}
Related
I like to have a Drive class where all files and folders for a project are managed.
My first attempt was pretty easy like a lot of functions (most of them with arguments).
Now I try to make it more fancy because it became more and more annoying to have a lot of functions, in which the desired one can be found. To not have an XY-problem here, I start with my dream.
I like to construct the Drive class in a way, so that it is super easy to find a certain file or folder.
If you look in the main function, I can find every needed file by writing a point and look which subclasses/methods are proposed to continue, till I find it and add .str to it. At every point, only the subclasses/methods will be proposed which makes sense at this point.
It almost works! It is more complicated to write and maintain as the first approach, but If I use it very often, it could be worth it.
I can:
go into subfolders
go into subfolders with name inside the argument
But there is an error if I define a fixed-name-subfolder of a fluid-name-folder like in the code below.
Now my questions:
how can I change the code so the main Function doesn't show this error?
would you recommend a completely different approach to the "make it easy to find strings inside a huge list of strings via making collections inside collections... of strings"-problem?
package utilities;
public class Drive_draft {
private static final String fs = System.getProperty("file.separator");
public static final String str = System.getProperty("user.home").concat(fs);
public static class IeCreation {
public static final String str = Drive_draft.str.concat(".meetings").concat(fs);
public static class Abstract {
public static final String str = IeCreation.str.concat("Abstracts").concat(fs);
}
public static class Meeting {
public static final String str = IeCreation.str.concat("Ueberordnungen").concat(fs);
}
}
public static class MetsSIPs {
public static final String str = Drive_draft.str.concat("workspace").concat(fs).concat("metsSIPs").concat(fs);
public static class preSIPs {
public static final String str = MetsSIPs.str.concat("preSIPs").concat(fs);
}
public static class RosettaInstance {
private static class MaterialflowId {
public static String str;
private static class ProducerId {
public static String str;
private static class Abstract {
public static String str;
public static class Mets {
public static final String str = Abstract.str.concat("content").concat(fs).concat("ie1.xml");
}
}
private static class Meeting {
public static String str;
}
public static Abstract Abstract (String value) {
Abstract ret = new Abstract();
ProducerId.Abstract.str = str.concat(value).concat(fs);
return ret;
}
public static Meeting Meeting (String value) {
Meeting ret = new Meeting();
ProducerId.Meeting.str = str.concat(value).concat(fs);
return ret;
}
}
public static ProducerId ProducerId (String value) {
ProducerId ret = new ProducerId();
MaterialflowId.ProducerId.str = str.concat(value).concat(fs);
return ret;
}
}
public static MaterialflowId MaterialflowId (String value) {
MaterialflowId ret = new MaterialflowId();
MaterialflowId.str = str.concat(value).concat(fs);
return ret;
}
}
public static class Dev extends RosettaInstance {
public static final String str = MetsSIPs.str.concat("dev").concat(fs);
}
public static class Test extends RosettaInstance {
public static final String str = MetsSIPs.str.concat("test").concat(fs);
}
public static class Prod extends RosettaInstance{
public static final String str = MetsSIPs.str.concat("prod").concat(fs);
}
}
#SuppressWarnings("static-access")
public static void main(String[] args) {
System.out.println(Drive_draft.MetsSIPs.Dev.str);
System.out.println(Drive_draft.MetsSIPs.Dev.MaterialflowId("1").str);
System.out.println(Drive_draft.MetsSIPs.Dev.MaterialflowId("2").str);
System.out.println(Drive_draft.MetsSIPs.Dev.MaterialflowId("1").ProducerId("t").str);
System.out.println(Drive_draft.MetsSIPs.Dev.MaterialflowId("1").ProducerId("t").Abstract("est").str);
System.out.println(Drive_draft.MetsSIPs.Dev.MaterialflowId("1").ProducerId("t").Meeting("oast").str);
System.out.println(Drive_draft.MetsSIPs.Dev.MaterialflowId("1").ProducerId("t").Abstract("est").Mets.str); //Error: Mets cannot be resolved or is not a field
}
}
You can encode your "directory" structure with interfaces, with each interface declaring what the user can do next. Then the implementation can use a StringBuilder to just append the appropriate snippets and keep returning this.
// PathBuilderInterfaces.java
public class PathBuilderInterfaces {
public interface Buildable {
String build();
}
public interface Drive extends Buildable {
IeCreation ieCreation();
MetsSIPs metsSIPs();
}
public interface IeCreation extends Buildable {
String ieCreationAbstract();
String meeting();
}
public interface MetsSIPs extends Buildable {
RosettaInstance dev();
RosettaInstance test();
RosettaInstance prod();
}
public interface RosettaInstance extends Buildable {
MaterialFlowId materialFlowId(String value);
}
public interface MaterialFlowId extends Buildable {
ProducerId producerId(String value);
}
public interface ProducerId extends Buildable {
Abstract producerIdAbstract(String value);
String meeting(String value);
}
public interface Abstract extends Buildable {
String mets();
}
}
// PathBuilder.java
import static com.example.somepackage.PathBuilderInterfaces.*;
public class PathBuilder implements Drive, IeCreation, MetsSIPs, RosettaInstance, MaterialFlowId, ProducerId, Abstract{
private StringBuilder builder = new StringBuilder(str);
private static final String fs = System.getProperty("file.separator");
public static final String str = System.getProperty("user.home").concat(fs);
public static Drive drive() {
return new PathBuilder();
}
#Override
public String build() {
return builder.toString();
}
#Override
public IeCreation ieCreation() {
builder.append(".meetings").append(fs);
return this;
}
#Override
public MetsSIPs metsSIPs() {
builder.append("workspace").append(fs).append("metsSIPs").append(fs);
return this;
}
#Override
public RosettaInstance dev() {
builder.append("dev").append(fs);
return this;
}
#Override
public RosettaInstance test() {
builder.append("test").append(fs);
return this;
}
#Override
public RosettaInstance prod() {
builder.append("prod").append(fs);
return this;
}
#Override
public MaterialFlowId materialFlowId(String value) {
builder.append(value).append(fs);
return this;
}
#Override
public ProducerId producerId(String value) {
builder.append(value).append(fs);
return this;
}
#Override
public Abstract producerIdAbstract(String value) {
builder.append(value).append(fs);
return this;
}
#Override
public String meeting(String value) {
builder.append(value).append(fs);
return build();
}
#Override
public String mets() {
builder.append("content").append(fs).append("ie1.xml");
return build();
}
#Override
public String ieCreationAbstract() {
builder.append("Abstracts").append(fs);
return build();
}
#Override
public String meeting() {
builder.append("Ueberordnungen").append(fs);
return build();
}
}
Usage:
// in a main method somewhere
System.out.println(
PathBuilder.drive()
.metsSIPs()
.dev()
.materialFlowId("1")
.producerId("t")
.producerIdAbstract("est")
.mets());
Here is my sample code
public class Example {
static interface Data {
}
static interface Source<D extends Data> {
public D read();
}
static class Stream<S extends Source<D>, D extends Data> {
public S source;
public Stream(S source){
this.source = source;
}
public D get() {
return this.source.read();
}
}
static class SampleData implements Data {
}
static class SampleSource implements Source<SampleData> {
#Override
public SampleData read() {
return null;
}
}
public static void main(String[] args) {
Stream sampleSourceStream = new Stream<SampleSource, SampleData>();
}
}
I want omit(for more beautiful structure/easy usage)
static class Stream<S extends Source<D>, D extends Data>
to
static class Stream<S extends Source<D>>
or
new Stream<SampleSource, SampleData>()
to
new Stream<SampleSource>()
(I know it can be omitted in C#...)
How can i omit or make more beautiful pattern?
Don't define S, it serves no purpose:
static class Stream<D extends Data> {
public Source<D> source;
public Stream(Source<D> source){
this.source = source;
}
public D get() {
return this.source.read();
}
}
public static void main(String[] args) {
SampleSource sampleSource = new SampleSource();
Stream<SampleData> sampleSourceStream = new Stream<>(sampleSource);
}
Or even simpler in Java 10+, using var:
public static void main(String[] args) {
SampleSource sampleSource = new SampleSource();
var sampleSourceStream = new Stream<>(sampleSource);
}
I have a class containing multiple constants and I would like to return all the constants except one in order to make some tests. I have made a simple method but it return the error "attribute value must be constant" when I use it in my annotation.
public final class RolesConstants {
public static final String APP_SYSTEM = "APP_SYSTEM";
public static final String APP_CLIENT = "APP_CLIENT";
public static final String APP_PROFESSIONAL = "APP_PROFESSIONAL";
public static final String APP_ADMIN = "APP_ADMIN";
public static final String PRO_ADMIN = "PRO_ADMIN";
public static final String PRO_ADD_BOOKING = "PRO_ADD_BOOKING";
public static final String PRO_EDIT_BOOKING = "PRO_EDIT_BOOKING";
...
public static String[] allRolesButAPP_SYSTEM() {
return new String[]{ APP_CLIENT, APP_PROFESSIONAL, ... };
}
}
import org.springframework.security.test.context.support.WithMockUser;
public class ProfessionalResourceIT {
#WithMockUser(roles = {RolesConstants.allRolesButAPP_SYSTEM()})
public void cannotGetIfNotSystem(){
assertThat(...);
}
}
attribute value must be constant
Could you try something like this
import org.springframework.security.test.context.support.WithMockUser;
public class ProfessionalResourceIT {
#WithMockUser(roles = {RolesConstants.APP_SYSTEM, RolesConstants.APP_CLIENT, so on})
public void cannotGetIfNotSystem(){
assertThat(...);
}
}
For example, I have such code:
SomeClass item = new SomeClass();
OtherClass.someVoidMethod(item); //there was some changes with item
and then in class, where was called method someVoidMethod(item) item will not change, cause we use in this method copy of that item. In C/C++ there is pointers. I'm looking for something like that in Java.
there is better example:
There i cant edit string from method
public class Main {
public static void main(String[] args) {
String string = "String";
changeIt(string);
System.out.println(string);
}
public static void changeIt(String string){
string = string + " edited";
}
And what suntax I need, to do that? I tied to use *string and so on, but i do this wrong.
i find that this code wil not work the way i want
public class Main {
public static void main(String[] args) {
SomeClass someClass = new SomeClass();
OtherClass.changeIt(someClass.getValue());
}
}
class SomeClass {
private String value;
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
}
class OtherClass {
public static void changeIt(String string){
string = "someStr";
}
}
so i need to use something like that:
public static void main(String[] args) {
SomeClass someClass = new SomeClass();
someClass.setValue(OtherClass.changeIt(someClass.getValue()));
}
public static String changeIt(String string){
return "someStr";
}
and there is no other way?
To make a Long Story short: use Parameters as Inputs to a method, and use the return value as Output. This will make your code better readable and easier to maintain.
For example:
public class Main {
public static void main(String[] args) {
String string = "String";
String modifiedString = changeIt(string);
System.out.println(modifiedString);
}
public static String changeIt(String string) {
return string + " edited";
}
}
If you wrap your string into a mutable Container, than you can modify it in your method. However for your example code I would strongly recommend to not use this Approach!
class StringContainer {
String content;
}
public class Main {
public static void main(String[] args) {
StringContainer container = new StringContainer();
container.content = "String";
changeIt(container);
System.out.println(container.content);
}
public static void changeIt(StringContainer container) {
container.content += " edited";
}
}
The StringBuilder, as mentioned by #aioobe, would also be a good alternative to use.
I am new to jmockit and trying to execute the following online example.
The #MockClass is not working. My BookStore's getBookTitle() method is calling the function of orginal class instead of the mock class.
BookStore class:
public class BookStore {
public String getBookTitle(String isbn){
return BookStoreService.getBookTitle(isbn);
}
}
BookStoreService class:
public class BookStoreService {
public static String getBookTitle(String isbn){
return "Random";
}
}
Test class:
public class BookStoreTest {
private static Map<String, String> bookMap = new HashMap<String, String>(2);
#BeforeClass
public static void setup() {
System.out.println("in setup()");
bookMap.put("0553293354", "Foundation");
bookMap.put("0836220625", "The Far Side Gallery");
}
#MockClass(realClass = BookStoreService.class)
public static class MockBookstoreService {
#Mock
public static String getBookTitle(String isbn) {
System.out.println("in getBookTitle()");
if (bookMap.containsKey(isbn)) {
return bookMap.get(isbn);
} else {
return null;
}
}
}
#Test
public void testGetBookTitle() throws Exception {
System.out.println("in testGetBookTitle()");
final String isbn = "0553293354";
final String expectedTitle = "Foundation";
BookStore store = new BookStore();
String title = store.getBookTitle(isbn);
System.out.println(title); // This prints "Random" instead of "Foundation"
Assert.assertEquals(title, expectedTitle);
}
}
PS: I am using TestNG
Using the latest stable version of jmockit you could do it like this:
#BeforeClass
public static void setup() {
System.out.println("in setup()");
bookMap.put("0553293354", "Foundation");
bookMap.put("0836220625", "The Far Side Gallery");
new MockUp<BookStoreService>() {
#Mock
public String getBookTitle(String isbn) {
System.out.println("in getBookTitle()");
if (bookMap.containsKey(isbn)) {
return bookMap.get(isbn);
} else {
return null;
}
}
};
}
Remove the obsolete block:
public static class MockBookstoreService{...}