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+====== HString ======
+**deep** was developed with efficiency and speed in mind. String handling in Java is not very efficient. However, strings are widely used in a compiler. Therefore, we don't use regular Java strings (''java.lang.String'') but implement an more efficient version (''ch.ntb.inf.deep.strings.HString''). This version should be used throughout the compiler whenever speed is important. //String// and //HString// differ in many aspects:
+  * A HString must be registered before it can be used. A table contains all the registered HStrings.
+  * A registered HString exists exactly once. If two HStrings like "Hello World" are created and registered both references point to the same HString-object!
+  * Two registered HStrings can be compared by comparing there references.
+  * Be careful: two HStrings can only be compared if they were registered before.
+  * The central HString-table is created once. If a project is recompiled already registered HStrings remain in the table.
+===== Implementation =====
+[{{ .:hstrings_uml.png?400 |Class diagramm for HStrings}}]
+Most strings contain characters which fit into 8 bit. If not 16 bits have to be used. This consumes more memory.
+===== Correct Use =====
+HStrings must be registered before they can be used. This is done with
+<code java>
+  HString.getRegisteredHString("...")
+</code>
+If a second HString with the same characters is created and registered both references point to the same HString. The comparison of two HStrings is way more efficient than with ''String.equals()''.
+**An example:**
+<code java>
+HString firstString = HString.getRegisteredHString("HelloWorld");
+HString secondString = HString.getRegisteredHString("test");
+if(firstString == secondString) {
+  // ...
+}
+</code>
+It's possible to compare to non-registered HStrings as well as comparing a registered with a non-registered HString. For this the class HString contains the method //equals//.
+<code java>
+HString firstString = HString.getRegisteredHString("one");
+HString secondString = HString.getHString("one");
+  firstString == secondString // evalutes to false
+  firstString.equals(secondString) // evalutes to true
+</code>

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