Topic 3 Java

Collection Heirarchy.

Question 2. String Interning.

String interning is a process of reusing strings to optimize memory usage. Strings are immutable in java in order to avoid the duplicate string with same value, Java uses string pool. String pool is a special area in the heap memory.

How string intern works.

A pool of unique string literals is maintained in the JVM. This pool is part of the heap memory often called the String Intern Pool or String Constant pool. We can manually ensure a string is part of the pool using the String.intern() method. String already present in the pool then the intern() returns a referenced to the pooled string. Not present then the string is added to the pool and the referenced to the pooled string is returned.

String str = "hello"; // Added to the pool
String str1 = "hello"; // Refering to the same object as str.
// str and str1 points to the same object inside the pool.
String str3 = new String("hello");
// String object is created inside the heap memory outside the pool.
// We can move it to the pool.
str3 = str3.intern(); // Add str3 to the pool or returns reference to the pooled string.

Comparison.

String s = "hello";
String str = new String("hello");
System.out.println(s==str1); // false different reference pool and heap.

str =str.intern(); // Now str is pointing to the pool string.
System.out.println(str1==str3);

When the string is interned then == is faster and string not interned then we have to use .equals

Question 3. How the @Autowired, @Resource and @Inject differs from each other.

Used for dependency injection and they differs in terms of usage, behaviour and source.