java java is an object-oriented programming (oop) language introduced by sun microsystems in 1995....
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JAVA
JAVA is an object-oriented programming (OOP) language introduced by Sun Microsystems in 1995.
In the Java programming language:A program is made up of one or more classesA class contains one or more methodsA method contains program statements
JAVA
Class with a method: class name
public class MyClass //class header{
private int myInt = 5; //instance variable
public double myMethod(int intParam) //method header
{// do stuff here
}
}
Class with a method:
public class myClass variable name initial value { type
private int myInt = 5; //instance variable
public double myMethod(int intParam){
// do stuff here}
}
JAVA
Class with a method:
public class myClass{
private int myInt = 5; //instance variable
return type name parameter type
public double myMethod(int intParam){
// do stuff here parameter name
return myVar; //return statement}
}
JAVA
JAVA
Java comments: Used to explain code. Ignored by the compiler
//single line comment.
/* multipleline comment*/
/**This is a javadoc comment*/
JAVA
The words used to program in Java (or any other language) are called identifiers. Java identifiers can be made of letters digits or the underscore character. They can not start with a number:
You should use JAVA conventions in naming your identifiers:Class names begin with a capital letter: MyClassVariable names begin with a lower case letter: myIntegerMethods begin with a lower case letter: myMethodConstants are all caps: MAXIMUM
JAVA
Many languages compile to run on a specific machine. The Java compiles the code to Java bytecode. A java interpreter installed on the machine running the program converts the Java bytecode to the machines native code. This lets a program written in Java run on multiple platforms. For instance a program compiled on a Linux machine can be run on a Microsoft machine. Java is considered to be architecture-neutral.
Java sourcecode
Machinecode
Javabytecode
Javainterpreter
Javacompiler
(x, y)
JAVA
Graphics in Java:
Horizontal (x) coordinates are measured from right.Vertical (y) coordinates are measured from top.
We are used to measuring vertical coordinates from the x-axis, so this can take some getting used to:
(x, y)
JAVA
Hello World!
Public class Test{
public static void main(String[] args) {
System.out.println(“Hello World!”);}
}
JAVA
Page 52: Programming Project 1.1 – 1.2
Page 48:1.13 – 1.17 self reviewPage 50: MC 1.6 – 1.8Page 51: Short Answer 1.7 – 1.9
JAVA
1.13 What is the difference between a high level language and a machine Language?
1.14 What is JAVA bytecode?
1.15 What is whitespace. Does it change program execution.
1.16 Which of the following are not valid JAVA identifiers?a)RESULT b) result c) 12345 d) x12345y e) black&white
f)answer_7
Page 51 1.8Why might the following valid JAVA identifiers not be good ones?a)q b) totVal c. theNextValueInTheList
Identify the following errors as compile-time, runtime, or logical:a)Multiplying two numbers when you meant to add themb)Dividing by zeroc)Forgetting a semi-colon at the end of a statementd)Spelling a word wrong in the output.e)Producing inaccurate resultsf)Typing “{“ when you should have typed “(“