Strings and the String Constant Pool
Explore how Java manages strings through immutability and the string constant pool, ensuring memory efficiency and thread safety. Learn to compare strings correctly and use StringBuilder for performance in string manipulation. This lesson prepares you to optimize text handling in Java applications and understand common interview questions on string processing.
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Strings are fundamental to nearly every Java application. Because they are used so heavily, the Java Virtual Machine (JVM) optimizes how they are stored and managed in memory. A core characteristic of Java Strings is immutability. Once a String object is created, its value cannot change. This immutability guarantees thread safety and allows the JVM to cache and reuse String instances safely.
We often encounter interview questions testing our understanding of how Java handles String memory allocation.
What is the difference between these two ways of creating a String?
String str1 = "Educative";
String str2 = new String("Educative");
What is the output of the following snippet, and why?
String obj1 = new String("abc");
String obj2 = new String("abc");
System.out.println(obj1 == obj2);
true, because both objects contain the same string value.
false, because new String() creates two different objects, and == compares object references.
true, because Java automatically interns all String objects created with new.
It prints false. As established, using new String("abc") forces two completely distinct String objects to be allocated on the heap. The == operator compares object references (memory identity), not the actual character contents. Since obj1 and obj2 point to different memory addresses, they are not strictly equal.
To compare the actual character content, we must always use the .equals() method. Had these variables been initialized as string literals (String a = "abc"; String b = "abc"; ...