Basic Java Language: Difference between revisions
wikademia>Lurkingfate →System.out: Cleaned up code examples |
wikademia>Lurkingfate →Asking the user: Cleaned up code examples. |
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The first way to get user input is from the keyboard without using the swing gui. You must first import the Scanner package first like so. <code>import java.util.Scanner;</code> Once you have done that you will have to create a Scanner object. <code>Scanner scan1 = new Scanner(System.in);</code> Finally after the user has entered the input asked for you retrieve using your Scanner object. For example if we wanted a string as input we could use the following code. | The first way to get user input is from the keyboard without using the swing gui. You must first import the Scanner package first like so. <code>import java.util.Scanner;</code> Once you have done that you will have to create a Scanner object. <code>Scanner scan1 = new Scanner(System.in);</code> Finally after the user has entered the input asked for you retrieve using your Scanner object. For example if we wanted a string as input we could use the following code. | ||
< | <source lang="java"> | ||
import java.util.Scanner; | import java.util.Scanner; | ||
Public class GettingStringInput | Public class GettingStringInput | ||
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Scanner scan1 = new Scanner(System.in); | Scanner scan1 = new Scanner(System.in); | ||
System.out.print("Please enter a string: "); | System.out.print("Please enter a string: "); | ||
yourinput = scan1.nextLine() | yourinput = scan1.nextLine(); | ||
} | } | ||
} | } | ||
</ | </source> | ||
''In order for the following to work properly, you must place the following code on the first line of your .java file. Importing packages will be explained later.'' | ''In order for the following to work properly, you must place the following code on the first line of your .java file. Importing packages will be explained later.'' | ||
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<code>import javax.swing.JOptionPane;</code> | <code>import javax.swing.JOptionPane;</code> | ||
Now, let's go on to asking the user to enter a number and doing calculations on it. Basically: < | Now, let's go on to asking the user to enter a number and doing calculations on it. Basically: <source lang="java">JOptionPane.showInputDialog( null, "Hello, enter something" );</source>. Try putting that in a class (in the main method, of course) and run it. Currently, we can't do anything with it because the value is deleted. | ||
Because what you enter can consist of letters OR numbers, and any length of them, what is "produced" by that is a String. The following will work: < | Because what you enter can consist of letters OR numbers, and any length of them, what is "produced" by that is a String. The following will work: <source lang="java">String mine = JOptionPane.showInputDialog( null, "Now I can set a String!" );</source>. Now lets say that after you get the string you want to print it. Just like regularly, add the following line: <source lang="java">System.out.println( mine );</source>. | ||
Now you probably want to be able to enter a number. Java provides a method of changing a '''String''' to an <code>int</code>. It is < | Now you probably want to be able to enter a number. Java provides a method of changing a '''String''' to an <code>int</code>. It is <source lang="java">Integer.parseInt( String_Here );</source>. So lets say you want the user to enter a number and you print it. Do: | ||
< | <source lang="java"> | ||
int mine = Integer.parseInt( JOptionPane.showInputDialog( null, "Now I can set an int!" ) ); | int mine = Integer.parseInt( JOptionPane.showInputDialog( null, "Now I can set an int!" ) ); | ||
System.out.println( mine ); | System.out.println( mine ); | ||
</ | </source> | ||
And now, of course, you can do whatever you want with that... | And now, of course, you can do whatever you want with that... | ||