Day-81,82 Strings in Java

What is a String in Java?

• A String is a sequence of characters.
• In Java, Strings are objects, not primitive types.
• The java.lang.String package provides the String class.
• The String class extends Object.
• Printing an object → internally calls toString().
• The String class overrides toString().

Creating Strings

1.Using String literal

   String name = "abc";  
   String name2 = "xyz";  

→ Stored in String pool. If another variable stores the same value, it points to the same object.

2.Using new keyword

   String name = new String("abc");  

→ Creates a new object in heap memory, even if the same value exists in String pool.

Properties of Strings

• String is immutable
• If we store another variable with the same value, it points to the same object in String pool.

• == vs equals()

  • == → compares memory reference.
  • .equals() → compares values (content)

Important String Methods

1. length() → get string size.
2. charAt(int) → access character at position.
3. substring(int, int) → extract part of string.
4. equals() → compare string values.
5. equalsIgnoreCase() → case-insensitive comparison.
6. compareTo() → lexicographic comparison (ASCII values).
7. toUpperCase()/ toLowerCase() → case conversion.
8. trim() → removes leading and trailing spaces.
9. replace(old, new) → replace characters (literal).
10. replaceAll(regex, replacement) → regex-based replacement.
11. split(String regex) → split string into array.
12. contains(CharSequence) → check substring.
13. startsWith() / endsWith() → check prefix/suffix.
14. intern() → returns string from string pool.