Learn Java Part 2
3 likes1,297 views
This document discusses the different types of tokens in Java including keywords, identifiers, literals, operators, and separators. It provides examples and details for each token type. Keywords such as if, else, class cannot be used as identifiers. Identifiers name variables and follow naming rules. Literals represent fixed values like integers and strings. Operators perform operations on operands like addition and comparison. Separators include braces, brackets, parentheses and terminators used in code blocks and expressions.
![{ } used to define block or to declare array with static elements
[ ] used to declare array variable
( ) used to define/call function or used in expressions
; used to terminate a statement
, used to separate variables in declaration
. used to access data members and member functions of an object or class](https://image.slidesharecdn.com/javappt2-150530135757-lva1-app6891/85/Learn-Java-Part-2-11-320.jpg)
Learn Java Part 2
- 1. Java Tokens: Keywords, Identifiers, Literals, Operators, and Seperators
- 2. A smallest individual unit in source code is known as Token Java Tokens Keywords Identifiers Literals Operators Seperators
- 3. Keywords are special tokens in the language which have reserved use in the language. Keywords may not be used as identifiers in Java — you cannot declare a field whose name is a keyword, for instance. Java has 50 keywords among which 48 are in use but 2 (goto and const) are currently not in use Here is a list of keywords in the Java programming language. You cannot use any of the following as identifiers in your programs. The keywords const and goto are reserved, even though they are not currently used. true, false, and null might seem like keywords, but they are actually literals; you cannot use them as identifiers in your programs. abstract continue for new switch assert*** default goto* package synchronized boolean do if private this break double implements protected throw byte else import public throws case enum**** instanceof return transient catch extends int short try char final interface static void class finally long strictfp** volatile const* float native super while * not used ** added in 1.2 *** added in 1.4 **** added in 5.0
- 4. Identifiers are the names of variables, methods, classes, packages and interfaces. • Don’t use a keyword • Don’t use a space • Don’t use a special symbol other than ( _ and $ ) • Cannot start with digit • Any length • If only a single word then use a lowercase • If more than one word then start first word with lowercase and other words start with first letter as Capital For example: int balance=500; //Single word int bankBalance=500; //Multiple Words
- 5. • Use lowercase For example: package pack1; package mypack1; • Every word start with first letter as Capital For example: class Balance{} class BankBalance{} • Use Uppercase and Underscore for separating the words For example: int PI=3.14; int MAX_VALUE=100;
- 6. Fixed value assigned to variables or used in expressions is known as Literals • Integer Literals: for example: 1, -2, 8523, -2105 etc. Data Type Size Range byte 1 Byte -27 to 27 -1 short 2 Bytes -215 to 215 -1 int 4 Bytes -231 to 231 -1 long 8 Bytes -263 to 263 -1 • Floating Literals: for example: 1.02, -2.689, 8523.369, 2105 etc. Data Type Size Range float 4 Byte -3.4 * 1038 to 3.4 * 1038 double 8 Bytes -1.7 * 10308 to 1.7 * 10308
- 7. • Character Literals: for example: ‘A’, ‘B’, ‘@’, ‘&’ etc. Data Type Size Range char 2 Bytes All Unicode characters • String Literals: for example: “Hello”, “Gurpreet Singh”, “ACET” etc. Data Type Size Range String 2 * No. of characters As much memory available • Boolean Literals: true and false. Data Type Size Range boolean 1 Byte true or false • Null Literals: null can be assigned to any reference type
- 8. Operators operates on operands. For example: In expression a+b , a & b are operands and + is operator • Arithmetic Operator: +, - , *, /, %. For example: 5+4 will result in 9 5-4 will result in 1 5*4 will result in 20 5/4 will result in 1 5%4 will result in 1 (remainder) -5%4 will result in -1 5%-4 will result in 1 -5%-4 will result in -1 Note: Sign of result in % operator depends on the sign of dividend(numerator) • Relational Operator: <, >, <=, >=, ==, != Output will be either true or false 5>6 will result in false 5>=6 will result in false (either greater than or equal to) 5<6 will result in true 5<=6 will result in true (either less than or equal to) 5==6 will result in false (equal to) 5!=6 will result in true (not equal to)
- 9. • Assignment Operator: = Assign the value on left hand side to right hand side. For example: A=10+5, will assign 15 to A • Logical Operator: returns true or false Logical AND (&&) Logical OR (||) Logical NOT (!) A B A&&B A||B !A true true true true false true false false true false false true false true true false false false false true • Increment/Decrement Operator: increases or decreases the value by 1 Pre-increment & Pre-decrement: ++a, --a Post-increment & Post-decrement: a++, a--
- 10. • Bitwise Operator: Performs operations on bits Bitwise AND(&) Bitwise OR(|) Bitwise XOR(^) Bitwise Complement or Not (!) A B A&B A|B A^B !A 0 0 0 0 1 1 0 1 0 1 0 1 1 0 0 1 0 0 1 1 1 1 1 0 • Shift Operator: shift the bits to left or right Left Shift(<<): shifts the bits to left and fill the vacant spaces with 0 Unsigned Right Shift(>>>): shifts the bits to right and fill the vacant spaces with 0 Signed Right Shift(>>): shifts the bits to right and fill the vacant spaces with leftmost bit, i.e. if leftmost bit is 0 then fill with 0, and if the leftmost bit is 1 then fill with 1 • Conditional(Ternary) Operator: Syntax: condition(relational expression) ? Expression 1 : Expression 2 If condition evaluates to true then result will be Expression 1 otherwise Expression 2
- 11. { } used to define block or to declare array with static elements [ ] used to declare array variable ( ) used to define/call function or used in expressions ; used to terminate a statement , used to separate variables in declaration . used to access data members and member functions of an object or class