String pool : separate memory structure inside a heap

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make a program more optimise

Strings are immutable we cannot change it we cannot change object

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comparison of string

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Create diff objects of Same value

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pretty printing in java

alt text output: 453.16f

‘%’ is called placeholder

System.out.printf("pie: %.3f", Math.PI);

output: 3.142

Here’s a tabular representation of the commonly used format specifiers in Java. These are used with methods like System.out.printf() or String.format() for formatted output:

Specifier	Description	Example	Output
`%d`	Integer (decimal)	`System.out.printf("%d", 42);`	`42`
`%f`	Floating-point number	`System.out.printf("%.2f", 3.14);`	`3.14`
`%e`	Scientific notation (lowercase)	`System.out.printf("%e", 12345.678);`	`1.234568e+04`
`%E`	Scientific notation (uppercase)	`System.out.printf("%E", 12345.678);`	`1.234568E+04`
`%c`	Character	`System.out.printf("%c", 'A');`	`A`
`%s`	String	`System.out.printf("%s", "Java");`	`Java`
`%b`	Boolean	`System.out.printf("%b", true);`	`true`
`%%`	Literal `%` symbol	`System.out.printf("%%");`	`%`
`%o`	Octal integer	`System.out.printf("%o", 10);`	`12` (octal)
`%x`	Hexadecimal integer (lowercase)	`System.out.printf("%x", 255);`	`ff` (hex)
`%X`	Hexadecimal integer (uppercase)	`System.out.printf("%X", 255);`	`FF` (hex)
`%t`	Date/Time specifier (see below)
`%n`	Newline character	`System.out.printf("Hello%nWorld");`	Multi-line

Additional Date/Time Specifiers (with `%t`)

Specifier	Description	Example	Output
`%tH`	Hour (24-hour format)	`System.out.printf("%tH", new Date());`	`14` (e.g., 2 PM)
`%tI`	Hour (12-hour format)	`System.out.printf("%tI", new Date());`	`02`
`%tM`	Minute	`System.out.printf("%tM", new Date());`	`30`
`%tS`	Second	`System.out.printf("%tS", new Date());`	`45`
`%tp`	AM/PM marker (lowercase)	`System.out.printf("%tp", new Date());`	`pm`
`%tB`	Full month name	`System.out.printf("%tB", new Date());`	`December`
`%tb`	Abbreviated month name	`System.out.printf("%tb", new Date());`	`Dec`
`%tA`	Full day name	`System.out.printf("%tA", new Date());`	`Friday`
`%ta`	Abbreviated day name	`System.out.printf("%ta", new Date());`	`Fri`
`%tY`	Year (4-digit)	`System.out.printf("%tY", new Date());`	`2024`
`%ty`	Year (last 2 digits)	`System.out.printf("%ty", new Date());`	`24`

Formatting Options

You can combine format specifiers with flags for more control:

Flag	Description	Example	Output
`-`	Left-align	`System.out.printf("%-10d", 123);`	`123`
`+`	Print sign for numbers	`System.out.printf("%+d", 123);`	`+123`
`0`	Pad with zeroes	`System.out.printf("%05d", 123);`	`00123`
`,`	Use grouping separator	`System.out.printf("%,d", 1234567);`	`1,234,567`
`.`	Precision for floating-point	`System.out.printf("%.2f", 3.14159);`	`3.14`

Example Program

import java.util.Date;

public class FormatSpecifierDemo {
    public static void main(String[] args) {
        System.out.printf("Integer: %d%n", 42);
        System.out.printf("Float: %.2f%n", 3.14159);
        System.out.printf("Character: %c%n", 'A');
        System.out.printf("String: %s%n", "Hello");
        System.out.printf("Hexadecimal: %x%n", 255);
        System.out.printf("Current Time: %tT%n", new Date());
    }
}