lab 01-2 objectives: writing a java program. how to send output to the command line console. ...
TRANSCRIPT
Lab 01-2
Objectives: Writing a Java program. How to send output to the command line
console. Learn about escape sequences. Learn how to compile, debug, and
execute a Java program.
Console Output
In Java, console output is achieved by calling System.out.print or System.out.println.
• The data to be output is given as an argument in parentheses.
System.out.println(“Blackjack”);
• Every invocation of println ends a line of output.
Blackjack_
Lab 01-3
println Versus print
The print method is like println, except that it does not end a line• With println, the next output goes on a new line
• With print, the next output goes on the same line
Lab 01-4
System.out.print(“Hello ”);
System.out.print(“World”);
Lab 01-5
The print Method
System.out.print(“Hello ”);
System.out.print(“World”);
Output
HelloWorld
Lab 01-6
The print Method
System.out.print(“Hello ”);
System.out.print(“World”);
Lab 01-7
The print Method
System.out.print(“Hello ”);
System.out.print(“World”);
Output
Hello World
Lab 01-8
The print Method
System.out.println(“Hello”);
System.out.println(“World”);
Lab 01-9
The println Method
System.out.println(“Hello”);
System.out.println(“World”);
Output
Hello
World
Lab 01-10
The println Method
21 is a Blackjack
7
7 is lucky
Lucky number 34
• A plus sign is used to connect more than one item
System.out.println(21 + “ is a Blackjack”);
System.out.println(3 + 4);
System.out.println(3 + 4 + “ is lucky”);
System.out.println(“Lucky number “ + 3 + 4);
The + Symbol
Lab 01-11
6
Error – the * symbol can not be used with Strings
7 is lucky
Error – the – symbol can not be used with Strings
3
• Be careful when using other math symbols.
System.out.println(3 * 2);
System.out.println(3 * “Hello World”);
System.out.println(11 – 4 + “ is lucky”);
System.out.println(“Lucky number “ + 11 - 4);
System.out.println(15 / 4);
Other Math Symbol
Lab 01-12
Escape Sequences
• Escape sequences are used to print characters that are non-printable. Escape sequences always begin with a \ (backslash) character.
• Common Escape sequences
\n – new line
\” – quote symbol
\t – tab
\\ - backslash
Lab 01-13
Escape Sequences (Cont…)
Output
Hello
World
Lab 01-14
System.out.println(“Hello\nWorld”);
Escape Sequences (Cont…)
System.out.println(“Hello\tWorld”);
Lab 01-15
Output
Hello World
Escape Sequences (Cont…)
System.out.println(“\”Hello\tWorld\””)
Lab 01-16
Output
“Hello World”
Normally program statements execute from top to bottom.
This is called sequential control. Sequential control is the default control structure.
There are other control structures that we will discuss later.
Lab 01-17
Sequential Programming
The order in which statements occur is important.
Sequential Programming (cont…)
What will be output by the following program segment?
System.out.print(“Chester ”); System.out.print(“Nimitz”);
Lab 01-18
OutputChester Nimitz
Sequential Programming (cont…)
Now what will be output by the following program segment?
System.out.print(“Chester\nNimitz”);
Lab 01-19
OutputChesterNimitz
Sequential Programming (cont…)
Now what will be output by the following program segment?
System.out.println(“Chester\\Nimitz”);
Lab 01-20
OutputChester\Nimitz
Sequential Programming (cont…)
Keep in mind as you are programming that where you place a statement determines when it will be executed.
SEQUENTIAL CONTROL
Lab 01-21
String Concatenation
System.out.print(“Hello ” + 1 + 2);
Lab 01-23
Here is a typical print statement.Here is a typical print statement.
String Concatenation (cont…)
System.out.print(“Hello ” + 1 + 2);
Lab 01-24
“Hello 1”“Hello 1”
System.out.print(“Hello ” + 1 + 2);
String Concatenation (cont…)
Lab 01-25
“Hello 1”“Hello 1”
“Hello 12”“Hello 12”
String Concatenation (cont…)
System.out.print(1 + 2 + “ Hello”);
Lab 01-26
Here is another typical print statement.Here is another typical print statement.
System.out.print(1 + 2 + “ Hello”);
String Concatenation (cont…)
Lab 01-27
33
System.out.print(1 + 2 + “ Hello”);
String Concatenation (cont…)
Lab 01-28
33
“3 Hello”“3 Hello”
String Concatenation (cont…)
System.out.print(“Hello ” + 3 * 2);
Lab 01-29
Here is another typical print statement.Here is another typical print statement.
String Concatenation (cont…)
System.out.print(“Hello ” + 3 * 2);
Lab 01-30
Multiplication has a higherprecedence than addition!Multiplication has a higherprecedence than addition!
String Concatenation (cont…)
System.out.print(“Hello ” + 3 * 2);
Lab 01-31
66
Sequential Programming (cont…)
System.out.print(“Hello ” + 3 * 2);
Lab 01-32
66
“Hello 6”“Hello 6”
String Concatenation (cont…)
System.out.print(“Hello ” + 6 - 4);
Lab 01-33
Here is another typical print statement.Here is another typical print statement.
String Concatenation (cont…)
System.out.print(“Hello ” + 6 - 4);
Lab 01-34
“Hello 6”“Hello 6”
String Concatenation (cont…)
System.out.print(“Hello ” + 6 - 4);
Lab 01-35
“Hello 6”“Hello 6”
Compile Time Error“operator - can not be applied to String, int”
Compile Time Error“operator - can not be applied to String, int”
System.out.print(“Hello ” + 6 - 4);
String Concatenation (cont…)
Lab 01-36
How can we “fix” this problem?How can we “fix” this problem?
System.out.print(“Hello ” + (6 - 4));
String Concatenation (cont…)
Lab 01-37
Use parantheses!Use parantheses!
System.out.print(“Hello ” + (6 - 4));
Sequential Programming (cont…)
Lab 01-38
22
System.out.print(“Hello ” + (6 - 4));
Sequential Programming (cont…)
Lab 01-39
22
“Hello 2”“Hello 2”
Lab 01-41
Start JCreator. Create a new file called “Lab01.java”. Save the new file in your Lab01 folder.
Top Down Design
Lab 01-42
Creating A Java Class File
Lab 01-43
Creating A Java Class File (cont…)
Lab 01-44
Creating A Java Class File (cont…)
Lab 01-45
Creating A Java Class File (cont…)
Lab 01-46
Creating A Java Class File (cont…)
Lab 01-47
Creating A Java Class File (cont…)
Class names should alwaysbegin with an uppercase letter.Class names should alwaysbegin with an uppercase letter.
Lab 01-48
Creating A Java Class File (cont…)
Click this button toset the location.Click this button toset the location.
Lab 01-49
Creating A Java Class File (cont…)
Lab 01-50
Creating A Java Class File (cont…)
public class Lab01{
}
Lab 01-51
Declaring A Java ClassThis class can be usedby other classes!This class can be usedby other classes!
public class Lab01{
}
Lab 01-52
Declaring A Java ClassThe keyword class definesthis file as a Java class.The keyword class definesthis file as a Java class.
public class Lab01{
}
Lab 01-53
Declaring A Java ClassUser defined name. Class names shouldalways begin with an uppercase letter.User defined name. Class names shouldalways begin with an uppercase letter.
public class Lab01{
}
Lab 01-54
Declaring A Java Class
The body of every class beginsand ends with a set of curly brackets.The body of every class beginsand ends with a set of curly brackets.
Lab 01-55
The main Method
• In Java, you need to have a method named main in at least one class.
• This method must appear within a class, but it can be any class.
• A class containing a main method is a program. Every program has a main method but not every class is a program.
public class Lab01{
public static void main(String[ ] args){
}}
Lab 01-56
The main Method (cont…)
Curly brackets are used to define blockstatements. Methods, like classes, areblock statements and must begin andend with a set of curly brackets.
Curly brackets are used to define blockstatements. Methods, like classes, areblock statements and must begin andend with a set of curly brackets.
public class Lab01{
public static void main(String[ ] args){
}}
Lab 01-57
The main Method (cont…)
The main method is static.The main method is static.
public class Lab01{
public static void main(String[ ] args){
System.out.println(“Main Method!”);}
}
Lab 01-58
The main Method (cont…)
Lab 01-59
Compiling A Java Class File
Lab 01-60
Compiling A Java Class File
Lab 01-61
Running A Java Program
Lab 01-62
Running A Java Program
public class Lab01{
public static void main(String[ ] args){
System.out.println(“Main Method!”);}
public void output() {System.out.println(“Hello World”);
}}
Lab 01-63
The main Method (cont…)
output is not staticoutput is not static
public class Lab01{
public static void main(String[ ] args){
System.out.println(“Main Method!”);}
public void output() {System.out.println(“Hello World”);
}}
Lab 01-64
The main Method (cont…)
Run the programRun the program
Lab 01-65
The main Method (cont…)
public class Lab01{
public static void main(String[ ] args){
System.out.println(“Main Method!”);}
public void output() {System.out.println(“Hello World”);
}}
Lab 01-66
The main Method (cont…)
output did not executeoutput did not execute
Lab 01-67
The main Method (cont…)
public class Lab01{
public static void main(String[ ] args){
}
public void output() {System.out.println(“Hello World”);
}}
Lab 01-68
The main Method (cont…)
How do we get from hereHow do we get from here
public class Lab01{
public static void main(String[ ] args){
}
public void output() {System.out.println(“Hello World”);
}}
Lab 01-69
The main Method (cont…)
How do we get from here to thereHow do we get from here to there
public class Lab01{
public static void main(String[ ] args){
output();}
public void output() {System.out.println(“Hello World”);
}}
Lab 01-70
The main Method (cont…)
A method call to outputA method call to output
Lab 01-71
The main Method (cont…)
Lab 01-72
The main Method (cont…)
Lab 01-73
The main Method (cont…)
error: non-static method output() cannot be referenced from a static context
error: non-static method output() cannot be referenced from a static context
Lab 01-74
The main Method (cont…)
Double click on the first line of the error.Double click on the first line of the error.
Lab 01-75
The main Method (cont…)The editor will send the cursor to
the line that contains the error.
The editor will send the cursor to the line that contains the error.
Static methods are class methods. Non-static methods are instance methods. Class methods can not call instance methods – however instance methods can call class methods. More on this topic later.
To be able to call output we need an instance of the class Lab01.
Lab 01-76
The main Method (cont…)
Lab 01-77
The main Method (cont…)
public class Lab01{
public static void main(String[ ] args){
Lab01 lab = new Lab01();
}
public void output() {System.out.println(“Hello World”);
}}
Lab 01-78
The main Method (cont…)
lab is an object. An object is an instance of a class.
lab is an object. An object is an instance of a class.
public class Lab01{
public static void main(String[ ] args){
Lab01 lab = new Lab01();lab.output();
}
public void output() {System.out.println(“Hello World”);
}}
Lab 01-79
The main Method (cont…)
We can call output using lab which is an instance of the class Lab01
We can call output using lab which is an instance of the class Lab01
Lab 01-80
Run The Program
public class Lab01{
public static void main(String[ ] args){
Lab01 lab = new Lab01();lab.output();
}
public void output() {System.out.println(“Hello\nWorld”);
}}
Lab 01-81
The main Method (cont…)
public class Lab01{
public static void main(String[ ] args){
Lab01 lab = new Lab01();lab.output();
}
public void output() {System.out.println(“Hello\\World”);
}}
Lab 01-82
The main Method (cont…)
public class Lab01{
public static void main(String[ ] args){
Lab01 lab = new Lab01();lab.output();
}
public void output() {System.out.println(“Hello World” + 1 + 2);
}}
Lab 01-83
The main Method (cont…)
public class Lab01{
public static void main(String[ ] args){
Lab01 lab = new Lab01();lab.output();
}
public void output() {System.out.println(1 + 2 + “Hello World”);
}}
Lab 01-84
The main Method (cont…)
Control Structures
Lab 01-85
Sequential ControlBranchingConditionsLooping
Lab 01-86
Control Structures
How The Program Executes.
Lab 01-87
public class Lab01{
public static void main(String[ ] args){
Lab01 lab = new Lab01();lab.output();
}
public void output() {System.out.println(1 + 2 + “Hello World”);
}}
Lab 01-88
The main Method (cont…)
public class Lab01{
public static void main(String[ ] args){
Lab01 lab = new Lab01();lab.output();
}
public void output() {System.out.println(1 + 2 + “Hello World”);
}}
Lab 01-89
The main Method (cont…)
public class Lab01{
public static void main(String[ ] args){
Lab01 lab = new Lab01();lab.output();
}
public void output() {System.out.println(1 + 2 + “Hello World”);
}}
Lab 01-90
The main Method (cont…)
public class Lab01{
public static void main(String[ ] args){
Lab01 lab = new Lab01();lab.output();
}
public void output() {System.out.println(1 + 2 + “Hello World”);
}}
Lab 01-91
The main Method (cont…)
public class Lab01{
public static void main(String[ ] args){
Lab01 lab = new Lab01();lab.output();
}
public void output() {System.out.println(1 + 2 + “Hello World”);
}}
Lab 01-92
The main Method (cont…)
public class Lab01{
public static void main(String[ ] args){
Lab01 lab = new Lab01();lab.output();
}
public void output() {System.out.println(1 + 2 + “Hello World”);
}}
Lab 01-93
The main Method (cont…)
public class Lab01{
public static void main(String[ ] args){
Lab01 lab = new Lab01();lab.output();
}
public void output() {System.out.println(1 + 2 + “Hello World”);
}}
Lab 01-94
The main Method (cont…)
public class Lab01{
public static void main(String[ ] args){
Lab01 lab = new Lab01();lab.output();
}
public void output() {System.out.println(1 + 2 + “Hello World”);
}}
Lab 01-95
The main Method (cont…)
Refers to the order in which the individual statements of a program are executed or evaluated
Lab 01-97
Control Structures
Lab 01-98
• Sequential (Default)• Branching• Conditional• Repetition (looping)
Control Structures
Sequential Control:Statements are executed in the order in which they are written.
Lab 01-99
Control Structures
System.out.println(“ABC”);System.out.println(“DEF”);
Lab 01-100
Control Structures
System.out.println(“ABC”);System.out.println(“DEF”);
Lab 01-101
Output:ABCDEF
Control Structures
Branching:Allows the flow of execution to jump to a different part of the program.
Lab 01-102
Control Structures
public static void main(String[] args) {Lab01 lab = new Lab01();lab.output();
}
public void output() {System.out.println(“Hello World”);
}
Lab 01-103
Control Structures
public void methodA() {methodB();methodC();
}
public void methodB() {System.out.print(“Hello ”);
}
public void methodC() {System.out.print(“World”);
}Lab 01-104
Control Structures
Questions?
Lab 01-105
