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import java.util.HashMap;
public class Library {
Library() {
}
public void getFinishedBooks(HashMap<String, Boolean> library) {
if(library.size() < 1)
System.out.println("Error! Library is empty.");
else {
for(String book : library.keySet()); {
if((library.get(book)) == true)
System.out.println(library.get(book));
}
}
}
public static void main(String[] args) {
HashMap<String, Boolean> myBooks = new HashMap<String, Boolean>();
myBooks.put("Road Down the Funnel", true);
myBooks.put("Rat: A Biology", false);
myBooks.put("TimeIn", true);
myBooks.put("3D Food Printing", false);
Library myLibrary = new Library();
myLibrary.getFinishedBooks(myBooks);
}
}
It's a basic library program. I can't seem to find what's causing the error...
Error message: "Error! Cannot find symbol if((library.get(book)) == true)
symbol: variable book
location: class Library
Remove the ; in the line
for(String book : library.keySet())
Its always better to use IDE when you start learning the language. Warnings in the IDE will help you solve the issue quickly.
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this is my second question, thankfully I resolved the first question I made. OK so this time I am having difficulty printing to the console this Main method and Duck class, I am supposed to print out "waddle waddle" and Quack into the console, I think its a problem with the refrence varible: any help will be greatly appreciated I alredy tried everything to get the code to run but the Java error said
"exit status 1;"cannot find symbol
String waddling = donald.waddle();
symbol: variable donald.
location: class Duck."
class Duck {
public String quack() {
return "*waddle waddle*";
}
#Override
public String toString() {
return "quack";
}
class Main {
public static void main(String[] args) {
class Duck {
public String waddle() {
return "*waddle waddle*";
String waddling = donald.waddle();
System.out.println(waddling);
}
}
}
}
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So that's my method and i got Main class from my teacher that uses this method and it should return only 1 Suspect but it returns the same one for 8 times or something i am really close on my deadline please help
public ArrayList<Suspect> getCommonPartners(Suspect aSuspect) {
ArrayList<Suspect> commonpartners = new ArrayList<>() ;
for(Suspect s: partners) {
for(Suspect sus: aSuspect.getPartners()) {
if(s.getCodename().equals(sus.getCodename())) {
commonpartners.add(s);
}
}
}
return (commonpartners);
}
Where is 'partners' coming from? You're running a for loop on it. Did you mean aSuspect?
If you are getting multiple of the same value. Do a check on the arraylist before adding it.
public ArrayList<Suspect> getCommonPartners(Suspect aSuspect) {
ArrayList<Suspect> commonpartners = new ArrayList<>() ;
for(Suspect s: partners) {
for(Suspect sus: aSuspect.getPartners()) {
if(s.getCodename().equals(sus.getCodename())) {
if(!commonpartners.contains(s)) {
commonpartners.add(s);
}
}
}
}
return (commonpartners);
}
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import java.util.*;
public class ass {
public static void main(String[] args) {
// TODO Auto-generated method stub
String[]c={"sid","is","cool"};
List<String>list1=new ArrayList<String>();
for(String w:c){
list1.add(w);
}
String[]q={"is"};
List<String>list2=new ArrayList<String>();
for(String t:q){
list2.add(t);
}
EditList(list1,list2);
for(int i=0;i<list1.size();i++){
System.out.printf("%s ", list1.get(i));
}
}
public static void EditList(Collection<String>l1, Collection<String>l2){
Iterator<String>it=l1.iterator();
while(it.hasNext()){
if(l2.contains(it.next()));
it.remove();
}
}
}
In this programme I have two lists. I wanted to remove the items that are common in the first and second list from the first list and print it. I don't want a workaround or any other code suggestions. Can someone please explain why my code is not working?
I am following New Boston's tutorials.
Here:
if(l2.contains(it.next()));
it.remove();
That semicolon after if is a real statement.
Thus it.remove() happens always; like if ... that if not there!
Thus the real answer: always always always use
if (){
stuff
}
... even for single statements! Same for loops!
try
public static void EditList(Collection<String>l1, Collection<String>l2){
Iterator<String>it=l1.iterator();
while(it.hasNext()){
String current=it.next();
if(l2.contains(current)){
i1.remove(current); // assuming u wish to remove from l1
}
}
}
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Closed 7 years ago.
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OK! I'm off to a flying STOP in my first java lesson. LOL
I'm getting this error:
# javac MyFirstApp.java
MyFirstApp.java:7: error: class, interface, or enum expected
}
^
1 error
From the below code.
public class MyFirstApp {
public static void main (String[] args) {
System.out.println("I Rule!");
System.out.println("The World");
}
}
}
And I'm pretty certain that I copied the example from the book exactly the way it was written. So where am I going wrong here?
Thanks
The compilation error exactly tells you where to look. MyFirstApp.java:7 implies there is something wrong at line 7. If you go through your code at line 7 there is an extra closing bracket. Remove this bracket and it would start compiling perfectly.
You have an extra closing brace }..
Try this..
public class MyFirstApp {
public static void main (String[] args) {
System.out.println("I Rule!");
System.out.println("The World");
}
}
There is an unpaired } in your code.
public class MyFirstApp {
public static void main (String[] args) {
System.out.println("I Rule!");
System.out.println("The World");
}
}
} // <-- Does not have a corresponding '{'
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In my main class I want to check if there was a change by using a boolean variable:
public class Main {
private boolean change = false;
public boolean getChange() {
return change;
}
public void setChange(boolean change) {
this.change = change;
}
private void method1() {
// some command
setChange(true);
method1();
}
If I want to get this boolean value in my second class, I always get returned "false", no matter if my method1 ran or not.
public class BoolTest {
Main m = new Main();
System.out.println(m.getChange()); // returns "false"
}
You must have two instances of Main. Use the same one. Example:
Main m = new Main();
System.out.println(m.getChange());
m.setChange(true);
System.out.println(m.getChange());
You probably want to share the same instance over multiple classes. Pass the instance to the other classes and use them as expected.