List search
In this chapter you will learn:
Does a List contain certain element
With List interface we can search to see if an element exist in it or not.
boolean contains(Object o)
Returns true if this list contains the specified element.boolean containsAll(Collection<?> c)
Returns true if this list contains all of the elements of the specified collection.
The following code creates a list and then inserts some string values
into the list. After printing out all of its values we use the contains
to see if the string "java2s.com" is in the list.
import java.util.ArrayList;
import java.util.List;
/*from ja va 2 s.c om*/
public class Main {
public static void main(String[] args) {
List list = new ArrayList();
list.add("1");
list.add("2");
list.add("3");
list.add("java2s.com");
System.out.println("List has:" + list);
boolean b = list.contains("java2s.com");
System.out.println(b);
}
}
The output:
Get the element index
We can search an element and look for its index in a List by using the following
methods. indexOf starts the search from the start of a list, while
lastIndexOf searches a value from the end of a list.
int indexOf(Object o)Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.int lastIndexOf(Object o)Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.
import java.util.ArrayList;
import java.util.List;
//from ja va 2 s .c o m
public class Main {
public static void main(String[] args) {
List list = new ArrayList();
list.add("1");
list.add("2");
list.add("3");
list.add("java2s.com");
System.out.println(list.indexOf("java2s.com"));
}
}
The output:
Next chapter...
What you will learn in the next chapter:
- How to use methods from List to get and set element
- How to replace an element in a List with set method
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