Searching in a ArrayList with custom objects for certain strings
JavaSearchArraylistCustom ObjectJava Problem Overview
I have a ArrayList with custom objects. I want to search inside this ArrayList for Strings.
The class for the objects look like this:
public class Datapoint implements Serializable {
private String stateBased;
private String name;
private String priority;
private String mainNumber;
private String groupadress;
private String dptID;
public Datapoint(){
}
public String getMainNumber() {
return mainNumber;
}
public void setMainNumber(String mainNumber) {
this.mainNumber = mainNumber;
}
public String getName() {
return name;
}
..and so on
I know how to search for a string in a ArrayList
ArrayList<String> searchList = new ArrayList<String>();
String search = "a";
int searchListLength = searchList.size();
for (int i = 0; i < searchListLength; i++) {
if (searchList.get(i).contains(search)) {
//Do whatever you want here
}
}
So I want to have a function to search in my ArrayList with for example five objects for all "name" strings.
Java Solutions
Solution 1 - Java
The easy way is to make a for
where you verify if the atrrtibute name
of the custom object have the desired string
for(Datapoint d : dataPointList){
if(d.getName() != null && d.getName().contains(search))
//something here
}
I think this helps you.
Solution 2 - Java
UPDATE: Using Java 8 Syntax
List<DataPoint> myList = new ArrayList<>();
//Fill up myList with your Data Points
List<DataPoint> dataPointsCalledJohn =
myList
.stream()
.filter(p-> p.getName().equals(("john")))
.collect(Collectors.toList());
If you don't mind using an external libaray - you can use Predicates from the Google Guava library as follows:
class DataPoint {
String name;
String getName() { return name; }
}
Predicate<DataPoint> nameEqualsTo(final String name) {
return new Predicate<DataPoint>() {
public boolean apply(DataPoint dataPoint) {
return dataPoint.getName().equals(name);
}
};
}
public void main(String[] args) throws Exception {
List<DataPoint> myList = new ArrayList<DataPoint>();
//Fill up myList with your Data Points
Collection<DataPoint> dataPointsCalledJohn =
Collections2.filter(myList, nameEqualsTo("john"));
}
Solution 3 - Java
try this
ArrayList<Datapoint > searchList = new ArrayList<Datapoint >();
String search = "a";
int searchListLength = searchList.size();
for (int i = 0; i < searchListLength; i++) {
if (searchList.get(i).getName().contains(search)) {
//Do whatever you want here
}
}
Solution 4 - Java
Probably something like:
ArrayList<DataPoint> myList = new ArrayList<DataPoint>();
//Fill up myList with your Data Points
//Traversal
for(DataPoint myPoint : myList) {
if(myPoint.getName() != null && myPoint.getName().equals("Michael Hoffmann")) {
//Process data do whatever you want
System.out.println("Found it!");
}
}
Solution 5 - Java
For a custom class to work properly in collections you'll have to implement/override the equals()
methods of the class. For sorting also override compareTo()
.
See this article or google about how to implement those methods properly.
Solution 6 - Java
contains()
method just calls equals()
on ArrayList
elements, so you can overload your class's equals()
based on the name
class variable. Return true
from equals()
if name
is equal to the matching String
. Hope this helps.
Solution 7 - Java
Use Apache CollectionUtils
:
CollectionUtils.find(myList, new Predicate() {
public boolean evaluate(Object o) {
return name.equals(((MyClass) o).getName());
}
}
Solution 8 - Java
String string;
for (Datapoint d : dataPointList) {
Field[] fields = d.getFields();
for (Field f : fields) {
String value = (String) g.get(d);
if (value.equals(string)) {
//Do your stuff
}
}
}
Solution 9 - Java
boolean found;
for(CustomObject obj : ArrayOfCustObj) {
if(obj.getName.equals("Android")) {
found = true;
}
}