Hash code in Java is very important specially with the introduction of the Java Collections API. Many classes in the Collections API uses hash code as a convention. So what exactly is a hash code? It is an integer representation of a specific Object instance. The assumption is that this integer value should be the same whenever the hashCode() method is invoked on the same Object more than once during an execution of a Java application. The Hashcode method must consistently provide the same value provided that no internal data used in equals is modified on the Object. We should not worry about this on Immutable objects as internal data is not change throughout it's lifetime. In addition, if two objects are equal using the equals method of the class, then the hashCode of both should return the same value. This implies that the hashCode should be based on the data used in equals method. Lastly, it is not required that two unequal Objects should have different hashCode. Since hashCode is common to all classes as it is implemented in the Object class, we will discuss on how it is implemented in the String class of Java. This post will explain and give examples on Java String Hashcode.