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ArrayList‘s indexOf method is used to find out first index of object in arraylist.
indexOf method takes object as argument and returns first occurrence of specified element.
Methods:
public int indexOf(Object o)
returns index of first occurrence of element in the ArrayList.
returns index of first occurrence of element in the ArrayList.
indexOf method return -1 if object is not present in the ArrayList
ArrayList indexOf Example:
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import java.util.ArrayList; import java.util.HashSet; import java.util.LinkedHashSet; import java.util.*; class IndexOfArrayListMain { /* * @author : Arpit Mandliya */ public static void main(String[] args) { ArrayList employeeNameList = new ArrayList(); employeeNameList.add("John"); employeeNameList.add("Ankit"); employeeNameList.add("Rohan"); employeeNameList.add("Amit"); System.out.println("Index of Ankit: "+employeeNameList.indexOf("Ankit")); System.out.println("*******************************"); System.out.println("Index of John: "+employeeNameList.indexOf("John")); System.out.println("*******************************"); // Arpit is not present in the list System.out.println("Index of Arpit: "+employeeNameList.indexOf("Arpit")); } } |
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Index of Ankit: 1 ******************************* Index of John: 0 ******************************* Index of Arpit: -1 |
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