Deep Knowledge about java. lang. String

String is a constant, and its object cannot be changed once it is created. When + is used to splice strings, A New String object is generated instead of appending content to the original String object. 1. String Pool (String Pool): String str3 = "bbb" is assigned to the String Pool. Step 1: Check whether the object "bbb" exists in the String Pool. If it does not exist, create a "bbb" object in the String Pool, and return the address of the "bbb" object in the String Pool to the referenced variable str3, in this way, str3 points to the "bbb" String object in the String Pool. Step 2: If the object exists, the object address is directly returned if it is not created. Note: String str4 = "bbb"; then modify str3 = "ccc"; a new one will be created without affecting str4. 2. For String str = new String ("aa"); a) First, find the String object "aa" in the String Pool. If yes, the "aa" object is not created in the String Pool, and an "aa" String object is directly created in the heap, then return the address of the "aa" object in the heap and assign it to the str reference. As a result, str points to the "aa" String object created in the heap. B) If no, create an "aa" object in the String Pool, and then create an "aa" object in the heap, then return the address of the "aa" object in the heap and assign it to the str reference. As a result, str points to the "aa" object created in the heap.