Java ArrayList indexOf() to get the position of first occurrence of input element inside the ArrayList

ArrayList.indexOf(element) Position ( Number ) of element present inside the ArrayList.
element : required, the element name.
It returns the position ( number ) of the first occurrence of the input element. -1 is returned if no matching element is found.

Examples with output

add()

ArrayList<String> languages = new ArrayList<String>();
languages.add("Java");
languages.add("PHP");
languages.add("Python");
System.out.println(languages.indexOf("PHP")); // 1
System.out.println(languages.indexOf("Python")); //2
System.out.println(languages.indexOf("HTML")); // -1

Output ( HTML is not present inside our ArrayList. )

1
2
-1

If multiple elements are present then first matching position is returned.

ArrayList<Integer> marks = new ArrayList<Integer>(3);
marks.add(55);
marks.add(54);
marks.add(55);
marks.add(54);
System.out.println(marks.indexOf(54)); //1

To get the last matching position of the element we can use lastIndexOf().

ArrayList Tutorials

add() contains() clear() clone() Java - Tutorials

Java

ArrayList.indexOf()

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