How To Prevent Duplicate Element Insertion In Arraylist In Java

arrayListObject.Index(“string”)

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class MyClass {
  public static void main(String[] args) throws java.lang.Exception {
    ArrayList < String > list = new ArrayList < String > ();
    list.add("Test");

    if (list.indexOf("Test") > -1) {
      System.out.println("Data already exists");
    }
  }
}

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