edit: The ArrayList wasn't needed to reproduce the "error". Sorry for this delay, but know it should be much clearer.
Why is:
c2.number.equals(c3.number) = false
I really expected a true here. There must be something wrong with my equals method?
Why on earth do I need to write more text...
package com.example.mypackage;
import java.util.ArrayList;
import java.util.Scanner;
class Contact {
public String name;
public String number;
public Contact(String name, String number) {
this.name = name;
this.number = number;
}
public void print(){
System.out.println(name+number);
}
#Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
} else if (obj == null) {
return false;
} else if (obj instanceof Contact) {
Contact contact = (Contact) obj;
if ((contact.name == this.name && contact.number == this.number)) {
return true;
}
}
return false;
}
}
public class Main {
private static Scanner scanner = new Scanner(System.in);
public static void main(String[] args) {
Contact c1 = new Contact("ben", "1");
c1.print();
Contact c2 = new Contact("ben", "1");
c2.print();
System.out.println("name : ");
String name=scanner.nextLine();
System.out.println("number");
String number=scanner.nextLine();
Contact c3=new Contact(name, number);
c3.print();
System.out.println("c1.equals(c2) = "+c1.equals(c2));
System.out.println("c3 instanceof Contact = "+(c3 instanceof Contact));
System.out.println("c2.name.equals(c3.name) = "+c2.name.equals(c3.name));
System.out.println("c2.number.equals(c3.number) = "+c2.number.equals(c3.number));
System.out.println("c2.number.equals(c3.number) = "+c3.equals(c2));
}
}
Output is:
ben1
ben1
name :
ben
number
1
ben1
c1.equals(c2) = true
c3 instanceof Contact = true
c2.name.equals(c3.name) = true
c2.number.equals(c3.number) = true
c2.number.equals(c3.number) = false
Process finished with exit code 0
Why is:
c2.number.equals(c3.number) = false
I really expected a true here. There must be something wrong with my equals method?
Why on earth do I need to write more text...
Why is:
c2.number.equals(c3.number) = false
I really expected a true here. There must be something wrong with my equals method?
Why on earth do I need to write more text...
Why is:
c2.number.equals(c3.number) = false
I really expected a true here. There must be something wrong with my equals method?
Why on earth do I need to write more text...
Ah finally I got it. The error is in the equals method.
I must use "equals()" instead of "==" there. For some reason this comparison does work with c1 and c2 but not with c3.
-1 is returned if it wasn't found in the list.
Did you forget to myList.add() it?
The only add I see is when you added c1.
You need to myList.add(c3) after you get the input, or it won't be in the list to find an index of.
Related
Let say we have an object:
#:checkDirty
class Test {
var a:Int;
var b(default, default):String;
var c(get, set):Array<Int>;
public function new() {
...
}
public function get_c() {
...
}
public function set_c(n) {
...
}
}
Could we write a macro checkDirty so that any change to field/properties would set property dirty to true. Macro would generate dirty field as Bool and clearDirty function to set it to false.
var test = new Test();
trace(test.dirty); // false
test.a = 12;
trace(test.dirty); // true
test.clearDirty();
trace(test.dirty); //false
test.b = "test"
trace(test.dirty); //true
test.clearDirty();
test.c = [1,2,3];
trace(test.dirty); //true
Just to note - whenever you consider proxying access to an object, in my experience, there are always hidden costs / added complexity. :)
That said, you have a few approaches:
First, if you want it to be pure Haxe, then either a macro or an abstract can get the job done. Either way, you're effectively transforming every property access into a function call that sets the value and also sets dirty.
For example, an abstract using the #:resolve getter and setter can be found in the NME source code, replicated here for convenience:
#:forward(decode,toString)
abstract URLVariables(URLVariablesBase)
{
public function new(?inEncoded:String)
{
this = new URLVariablesBase(inEncoded);
}
#:resolve
public function set(name:String, value:String) : String
{
return this.set(name,value);
}
#:resolve
public function get(name:String):String
{
return this.get(name);
}
}
This may be an older syntax, I'm not sure... also look at the operator overloading examples on the Haxe manual:
#:op(a.b) public function fieldRead(name:String)
return this.indexOf(name);
#:op(a.b) public function fieldWrite(name:String, value:String)
return this.split(name).join(value);
Second, I'd just point out that if the underlying language / runtime supports some kind of Proxy object (e.g. JavaScript Proxy), and macro / abstract isn't working as expected, then you could build your functionality on top of that.
I wrote a post (archive) about doing this kind of thing (except for emitting events) before - you can use a #:build macro to modify class members, be it appending an extra assignment into setter or replacing the field with a property.
So a modified version might look like so:
class Macro {
public static macro function build():Array<Field> {
var fields = Context.getBuildFields();
for (field in fields.copy()) { // (copy fields so that we don't go over freshly added ones)
switch (field.kind) {
case FVar(fieldType, fieldExpr), FProp("default", "default", fieldType, fieldExpr):
var fieldName = field.name;
if (fieldName == "dirty") continue;
var setterName = "set_" + fieldName;
var tmp_class = macro class {
public var $fieldName(default, set):$fieldType = $fieldExpr;
public function $setterName(v:$fieldType):$fieldType {
$i{fieldName} = v;
this.dirty = true;
return v;
}
};
for (mcf in tmp_class.fields) fields.push(mcf);
fields.remove(field);
case FProp(_, "set", t, e):
var setter = Lambda.find(fields, (f) -> f.name == "set_" + field.name);
if (setter == null) continue;
switch (setter.kind) {
case FFun(f):
f.expr = macro { dirty = true; ${f.expr}; };
default:
}
default:
}
}
if (Lambda.find(fields, (f) -> f.name == "dirty") == null) fields.push((macro class {
public var dirty:Bool = false;
}).fields[0]);
return fields;
}
}
which, if used as
#:build(Macro.build())
#:keep class Some {
public function new() {}
public var one:Int;
public var two(default, set):String;
function set_two(v:String):String {
two = v;
return v;
}
}
Would emit the following JS:
var Some = function() {
this.dirty = false;
};
Some.prototype = {
set_two: function(v) {
this.dirty = true;
this.two = v;
return v;
}
,set_one: function(v) {
this.one = v;
this.dirty = true;
return v;
}
};
I need to know, what would be proper way to implement Maps with 64 bit keys. There will not be so many items in them, I just need to use various bits of the key for various things with large enough address space and I need it to be very fast, so String keys would probably be too slow. So far I tried:
import haxe.Int64;
import haxe.Unserializer;
import haxe.Serializer;
class Test {
static function main () {
var key:Int64 = 1 << 63 | 0x00000001;
var omap:Map<Int64, String> = new Map<Int64, String>();
omap.set(key, "test");
var smap:Map<Int64, String> = Unserializer.run(Serializer.run(omap));
var key2:Int64 = 1 << 63 | 0x00000001;
trace(key+" "+smap.get(key2));
}
}
http://try.haxe.org/#7CDb2
which obviously doesn't work, because haxe.Int64 creates an object instance. Using cpp.Int64 works, because it for some reason falls back to 32 bit integer in my cpp code and I don't know what am I doing wrong. How can I force it to "stay" 64 bit, or should I do it some other way?
EDIT: This is currently not working on native targets due to bug / current implementation in hxcpp: https://github.com/HaxeFoundation/hxcpp/issues/523
I figured out this workaround / wrapper, which may not be the most efficient solution possible, but it seems to work.
import haxe.Int64;
import haxe.Unserializer;
import haxe.Serializer;
class Test {
static function main () {
var key:Int64 = Int64.make(1000,1);
var omap:Int64Map<String> = new Int64Map();
omap.set(key, "test");
var smap:Int64Map<String> = Unserializer.run(Serializer.run(omap));
var key2:Int64 = Int64.make(1000,1);
trace(key+" "+smap.get(key2));
}
}
class Int64Map<V> {
private var map:Map<Int64,V>;
public function new() : Void {
this.map = new Map<Int64,V>();
}
public function set(key:Int64, value:V):Void {
this.map.set(key, value);
}
public inline function get(key:Int64):Null<V> {
var skey:Null<Int64> = getMapKey(key);
if (skey != null) return this.map.get(skey);
return null;
}
public inline function exists(key:Int64):Bool {
return (getMapKey(key) != null);
}
public function remove( key : Int64 ) : Bool {
var skey:Null<Int64> = getMapKey(key);
if (skey != null) return this.map.remove(skey);
return false;
}
public function keys() : Iterator<Int64> {
return this.map.keys();
}
public function toString() : String {
return this.map.toString();
}
public function iterator() : Iterator<V> {
return this.map.iterator();
}
private function getMapKey(key:Int64):Null<Int64> {
for (ikey in this.map.keys()){
if (Int64.eq(key, ikey)){
return ikey;
}
}
return null;
}
}
http://try.haxe.org/#57686
im trying to display a boolean value as a string in a tableview so instead of true i want to display male.
i'm a bit lost with it to be honest. i cant find anything on the internet to help.
the error ecilpse is giving me is The method " setCellValueFactory(Callback,ObservableValue>) in the type TableColumn is not applicable for the arguments (( cellData) -> {})"
heres my code. its probably wrong
TableColumn<Animal, String > genColumn = new TableColumn<>("Male");
genColumn.setMinWidth(50);
genColumn.setCellValueFactory(cellData -> {
boolean gender = cellData.getValue().getGender();
String genderAsString;
if(gender == true)
{
genderAsString = "Male";
}
else
{
genderAsString = "Female";
}
new ReadOnlyStringWrapper(genderAsString);
});
i would be grateful for any help thanks
Keep the type as boolean and use a cell factory to change the way you display it:
TableColumn<Animal, Boolean> genColumn = new TableColumn<>("Gender");
genColumn.setCellValueFactory(cellData -> cellData.getValue().genderProperty());
// or cellData -> new SimpleBooleanProperty(cellData.getValue().getGender())
// if your model class doesn't use JavaFX properties
genColumn.setCellFactory(col -> new TableCell<Animal, Boolean>() {
#Override
protected void updateItem(Boolean item, boolean empty) {
super.updateItem(item, empty) ;
setText(empty ? null : item ? "Male" : "Female" );
}
});
i managed to get it working i was just missing the return statement.
heres the code
TableColumn<Animal, String > genColumn = new TableColumn<>("Gender");
genColumn.setMinWidth(50);
genColumn.setCellValueFactory(cellData -> {
boolean gender = cellData.getValue().getGender();
String genderAsString;
if(gender == true)
{
genderAsString = "Male";
}
else
{
genderAsString = "Female";
}
return new ReadOnlyStringWrapper(genderAsString);
});
Lab Description : Compare two strings to see if each of the two strings contains the same letters in the
same order.
This is what I have so far far:
import static java.lang.System.*;
public class StringEquality
{
private String wordOne, wordTwo;
public StringEquality()
{
}
public StringEquality(String one, String two)
{
setWords (wordOne, wordTwo);
}
public void setWords(String one, String two)
{
wordOne = one;
wordTwo = two;
}
public boolean checkEquality()
{
if (wordOne == wordTwo)
return true;
else
return false;
}
public String toString()
{
String output = "";
if (checkEquality())
output += wordOne + " does not have the same letters as " + wordTwo;
else
output += wordOne + " does have the same letters as " + wordTwo;
return output;
}
}
My runner looks like this:
import static java.lang.System.*;
public class StringEqualityRunner
{
public static void main(String args[])
{
StringEquality test = new StringEquality();
test.setWords(hello, goodbye);
out.println(test);
}
}
Everything is compiling except for the runner. It keeps saying that hello and goodbye aren't variables. How can I fix this so that the program does not read hello and goodbye as variables, but as Strings?
You need to quote strings otherwise they are treated as variables.
"hello"
"goodbye"
so this would work better.
test.setWords("hello", "goodbye");
Problem with your code is with checkEquality(), you are comparing the string's position in memory when you use == use .equals() to check the string
public boolean checkEquality()
{
if (wordOne == wordTwo) //use wordOne.equals(wordTwo) here
return true;
else
return false;
}
Enclose them in double-quotes.
I would like to create a method that orders an IEnumerable List by a given property where the property is passed into the method by a string i.e. (Mind you the first code example does not work, but the second does and is what I am trying to emulate dynamically).
string sortName = "SerialNumber";
IEnumerable<PartSummary> partList = FunctionToCreateList();
partOrderedList = partList.OrderBy(what do I stick in here);
that would be equivalent to
IEnumerable<PartSummary> partList = FunctionToCreateList();
partOrderedList = partList.OrderBy(p => p.SerialNumber);
How can I accomplish this?
Are you saying you want to pass the order by in to your method? If so, you can use this:
Expression<Func<PartSummary, bool>> orderByClause
Then you can do this:
partOrderedList = partList.OrderBy(orderByClause);
Then you can handle your order by in your business layer or wherever you wish.
Okay, update: If you want to pass in the column name as a string you can do something like as follows:
Create a static class for an extension method (reference: http://social.msdn.microsoft.com/Forums/en-US/linqprojectgeneral/thread/39028ad2-452e-409f-bc9e-d1b263e921f6/):
static class LinqExtensions
{
public static IQueryable<T> OrderBy<T>(this IQueryable<T> source, string sortingColumn, bool isAscending)
{
if (String.IsNullOrEmpty(sortingColumn))
{
return source;
}
ParameterExpression parameter = Expression.Parameter(source.ElementType, String.Empty);
MemberExpression property = Expression.Property(parameter, sortingColumn);
LambdaExpression lambda = Expression.Lambda(property, parameter);
string methodName = isAscending ? "OrderBy" : "OrderByDescending";
Expression methodCallExpression = Expression.Call(typeof(Queryable), methodName,
new Type[] { source.ElementType, property.Type },
source.Expression, Expression.Quote(lambda));
return source.Provider.CreateQuery<T>(methodCallExpression);
}
}
Then you can create your method:
static IQueryable<PartSummary> FunctionToCreateList()
{
IList<PartSummary> list = new List<PartSummary>();
list.Add(new PartSummary
{
Id = 1,
SerialNumber = "A",
});
list.Add(new PartSummary
{
Id = 2,
SerialNumber = "B",
});
return list.AsQueryable();
}
And then call your method:
static void Main(string[] args)
{
IQueryable<PartSummary> partOrderedList = FunctionToCreateList();
PartSummary partSummary = new PartSummary();
string sortBy = "Id";
partOrderedList = partOrderedList.OrderBy(sortBy, false);
foreach (PartSummary summary in partOrderedList)
{
Console.WriteLine(summary.Id + ", " + summary.SerialNumber);
}
Console.ReadLine();
}
Now you can pass in the column name as a string and sort.
Hope this helps!
You can also avoid extending and just use a compiled expression tree to accomplish this:
public Func<T, object> ResolveToProperty<T>(String propertyName)
{
Type t = typeof(T);
var paramExpression = Expression.Parameter(t, "element");
var propertyExpression = Expression.Property(paramExpression, propertyName);
return Expression.Lambda<Func<T, object>>(propertyExpression, paramExpression).Compile();
}
string sortName = "SerialNumber";
IEnumerable<PartSummary> partList = FunctionToCreateList();
var partOrderedList = partList.OrderBy(ResolveToProperty<PartSummary>(sortName));