need of overriding equals method in java code example

Example: overriding equals method in java

1.	public class Test
2.	{
3.		private int num;
4.		private String data;
5.
6.		public boolean equals(Object obj)
7.		{
8.			if(this == obj)
9.				return true;
10.			if((obj == null) || (obj.getClass() != this.getClass()))
11.				return false;
12.			// object must be Test at this point
13.			Test test = (Test)obj;
14.			return num == test.num &&
15.			(data == test.data || (data != null && data.equals(test.data)));
16.		}
26.		// other methods
27.	}