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Questions and Answers
What punctuation mark ends an assignment statement?
Which type of value cannot be directly assigned to an int variable without a cast?
What is the process called when assigning a value to a variable in Java?
What is an item in Java with one specific value that cannot change?
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Which type of constants may not be written with a decimal point in Java?
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In Java, which type cannot be directly assigned to a variable of type boolean?
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What is the purpose of declaring a variable in Java?
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Which of the following is an invalid identifier in Java?
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What is the purpose of the assignment operator (=) in Java?
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What is the correct syntax for declaring multiple variables of the same type in Java?
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Which of the following is a valid identifier in Java?
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What is the purpose of keywords in Java?
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Study Notes
Identifiers in Java
- A Java identifier is the name of a variable or other item defined in a program.
- An identifier must not start with a digit and can only contain letters, digits, or the underscore (_) symbol.
- The symbol $ is also allowed, but it's reserved for special purposes only.
Keywords in Java
- Keywords are a special class of identifiers with a predefined meaning in Java.
- Keywords cannot be used as names for variables or anything else.
Variables and Declaration
- Every variable in a Java program must be declared before it is used.
- When declaring a variable, you specify the type of data it will store.
- Syntax:
Type Variable_1, Variable_2,...; - Examples:
int count, number;,char answer;,double speed, distance;
Primitive Datatypes
- No specific details mentioned in the text.
Assignment Statements
- The equal sign (=) is used as the assignment operator.
- An assignment statement always consists of a variable on the left-hand side and an expression on the right-hand side.
- An assignment statement ends with a semicolon.
- The expression on the right-hand side can be a variable, a number, or a complicated expression.
- Examples:
distance = rate * time;,count = count + 2;
Assignment Statements with Primitive Types
- When a variable of a primitive type is on the left-hand side of an assignment, the expression on the right-hand side is evaluated first.
- Then, the variable is set equal to the evaluated value.
Initializing Variables
- Assigning a value to a variable is known as initialization.
- Combine the declaration and an assignment statement, e.g.,
int count = 0;,double speed = 65.5;,char grade = 'A';
Short Hand Assignments operators
- No specific details mentioned in the text.
Assignment Compatibility
- In general, a value of one type cannot be stored in a variable of another type.
- Exceptions: an int value can be stored in a double type.
- A value of any type can be assigned to a variable of any type that appears to the right of it in the list:
byte,short,int,long,float,double,char. - An explicit type cast is required to assign a value of one type to a variable whose type appears to the left of it on the list (e.g., double to int).
Constants
- A constant (or literal) is an item in Java with a specific value that cannot change.
- Constants of an integer type cannot be written with a decimal point.
- Constants of a floating-point type can be written in ordinary decimal fraction form or in scientific notation.
- Constants of type char are expressed by placing a single character in single quotes.
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Description
Test your knowledge on Java identifiers, variables, and assignments. Learn about the rules and conventions for defining identifiers in Java, including restrictions on the use of digits and special characters.
