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Java A - 1
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Java A - 2
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Java A - 3
Java A - 4
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Java A - 5
public class Hej
{
public static void main(String[] args)
{
System.out.println("Hej på dig!");
}
}
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Java A - 6
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==> java Hej
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float
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Java A - 7
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Java A - 8
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public class Cirkel
{
public final double pi = 3.14159;
private double radie = 0;
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public Cirkel(double r)
{
radie = r;
}
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rutan
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public double yta()
{
return radie * radie * pi;
}
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public static void main(String[] args)
{
Cirkel enCirkel = new Cirkel(10.0);
Kvadrat
rutan = new Kvadrat(12);
System.out.println(enCirkel.yta());
•
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}
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Java A - 10
//Fil: Cirkel.java
//Fil: Kvadrat.java
public class Cirkel
public class Kvadrat
{
{
public final double pi = 3.14159;
private double sida = 0;
private double radie = 0;
public Kvadrat(double a)
public Cirkel(double r)
{
{
sida = a;
radie = r;
}
}
public double yta()
public double yta()
{
{
return sida * sida;
return radie * radie * pi;
}
}
}
public static void main(String[] args)
{
Cirkel enCirkel = new Cirkel(10.0);
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System.out.println(enCirkel.yta());
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}
}
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public class Main //Fil: Main.java
{
public static void main(String[] args)
{
Kvadrat kvadraten = new Kvadrat(3.0);
Cirkel cirkeln = new Cirkel(10.0);
System.out.println(kvadraten.yta());
System.out.println(cirkeln.yta());
}
}
==> javac -g Main.java Kvadrat.java Cirkel.java
==> java Main
9.0
314.159
==>
==> javac -g Main.java
==> java Main
9.0
314.159
==>
Java A - 11
Java A - 12
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//Fil: MinaKlasser.java
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class Cirkel
{
public final double pi = 3.14159;
private double radie = 0;
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public class Kvadrat
{
private double sida = 0;
public Cirkel(double r)
{
radie = r;
}
public Kvadrat(double sida)
{
this.sida = sida;
}
public double yta()
{
return radie * radie * pi;
}
}
public static void main(String[] args)
{
Cirkel enCirkel = new Cirkel(10.0);
•
System.out.println(enCirkel.yta());
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}
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}
class Main
{
public static void main(String[] args)
{
Kvadrat kvadraten = new Kvadrat(3.0);
Cirkel cirkeln = new Cirkel(10.0);
System.out.println(kvadraten.yta());
System.out.println(cirkeln.yta());
}
}
==> javac -O MinaKlasser.java
==> java Main
9.0
314.159
==> ls *.class
Kvadrat.class Cirkel.class Main.class
public class Kvadrat
{
private double sida = 0;
public Kvadrat()
{
this(7.0); // Får endast förekomma på den
}
// första raden
public Kvadrat(double sida)
{
this.sida = sida;
}
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Java A - 13
Java A - 14
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for (int i=0; i<10; i++)
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summa += i;
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System.out.println(summa);
System.out.println(i);
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Java A - 15
Java A - 16
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super
public class Kvadrat
{
private static int antalInstanser = 0;
private double sida = 0;
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public Kvadrat(double a)
{
sida = a;
antalInstanser++;
}
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public static void main(String[] args)
{
System.out.println(antalInstanser);
Kvadrat rutan = new Kvadrat(4.2);
System.out.println(antalInstanser);
}
}
8WVNULIW
==> java Kvadrat
0
1
==>
Java A - 17
Java A - 18
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public class Kvadrat
{
private static int antalInstanser = 0;
private double sida = 0;
•
intArray NDQ
intArray = new int[10];
•
public Kvadrat(double a)
{
sida = a;
antalInstanser++;
}
}
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public static int antal()
{
return antalInstanser;
}
public static void main(String[] args)
{
System.out.println(Kvadrat.antal());
Kvadrat rutan = new Kvadrat(4.2);
System.out.println(rutan.antal());
rutan = new Kvadrat(4.2);
System.out.println(antal());
}
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double
double[] tal = new double[3];
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8WVNULIW
==> java Kvadrat
0
1
2
==>
.YDGUDW[]
rutor = new Kvadrat[];
Java A - 19
Java A - 20
0HUDRPIlOW
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public class Kvadrat
{
private double sida = 0;
public Kvadrat(double a)
{
sida = a;
}
8WVNULIW
==> java Kvadrat
20.0
4.41
2
4.0
==>
public double yta()
{
return sida * sida;
}
public static void main(String[] args)
{
double decimalTal[] = new double[2];
decimalTal[0] = 10;
decimalTal[1] = 20;
Kvadrat[] ruta = new Kvadrat[2];
ruta[0] = new Kvadrat(1.5);
ruta[1] = new Kvadrat(2.1);
System.out.println(decimalTal[1]);
System.out.println(ruta[1].yta());
/*************************************************
* Fält kan även initieras på följande sätt!
* Metoden kan dock inte användas för att tilldela
* elementen i ett redan existerande fält andra
* värden
**************************************************/
int[] helTal = {1, 2, 3};
Kvadrat[] fyrkant = {new Kvadrat(1), new Kvadrat(2)};
System.out.println(helTal[1]);
System.out.println(fyrkant[1].yta());
}
}
typ[] f;
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typ[] f = {värde, värde, ... , värde};
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f = new typ[]{värde, värde, ..., värde};
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Java A - 21
Java A - 22
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public class Tal
{
private int tal = 0;
•
/* Varför fungerar inte denna funktion?
static void swap(Tal tal1, Tal tal2)
{
Tal temporärReferens = tal1;
•
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tal1 = tal2;
tal2 = temporärReferens;
}
•
*/
HWW Q\WW REMHNW
static void swap(Tal[] par)
{
Tal temporärReferens = par[0];
String s1 = ”Musse ”;
String s2 = ”Pigg”;
par[0] = par[1];
par[1] = temporärReferens;
// s1 och s2 slås ihop, resultatet sparas i s3
String s3 = s1.concat(s2);
//s3 == ”Musse Pigg”
}
public static void main(String[] args)
{
Tal a = new Tal();
Tal b = new Tal();
a.tal = 1;
b.tal = 2;
//swap(a, b);
//En modifierad kopia av s1 tilldelas s4
String s4 = s1.toLowerCase(); //s4 == ”musse”
•
Fungerar inte!
swap(tal);
a = tal[0];
b = tal[1];
System.out.println(a.tal);
System.out.println(b.tal);
}
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String s = ”abcde”.substring(1,3);
Tal[] tal = {a, b};
}
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//s == "bc"
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String s1 = ”Kalle ”;
String s2 = ”Anka”;
String s = s1 + s2 + ”!”;
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public class StringDemo
{
public static void main(String[] argument)
{
String namn = "
Kalle Anka´s lyckotal är 13
Java A - 23
0HWRGHULNODVVHQ6WULQJ
([HPSHO Sn QnJUD NRQVWUXNWRUHU
";
//trim() rensar bort inledande och avslutande blanktecken
namn = namn.trim();
String kalle = "Kalle";
String ankas = "Anka´s";
String kAnka = kalle + ' ' + ankas + " lyckotal är " + 13;
System.out.println((namn == kAnka) ? "Lika" : "Ej lika");
System.out.println((namn.equals(kAnka)) ? "Lika" : "Ej lika");
}
}
public class ByteDemo
{
public static void main(String[] argument)
{
byte[] byteData = "ÅÄÖåäö".getBytes();
for (int i=0; i<byteData.length; i++)
System.out.println(byteData[i]);
String åäöSträngen = new String(byteData);
System.out.println(åäöSträngen);
}
}
public class ArgDemo
{
public static void main(String[] argument)
{
for (int i=0; i<argument.length; i++)
System.out.println(argument[i]);
}
}
Java A - 24
==> java ByteDemo
-59
-60
-42
-27
==> java StringDemo ==> java ArgDemo Grodan Boll -28
-10
Grodan
Ej lika
ÅÄÖåäö
Boll
Lika
==>
==>
==>
String()
String(String value)
String(char[] value)
String(byte[] value)
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char charAt(int index)
int compareTo(String anotherString)
boolean equals(Object anObject)
byte[] getBytes()
int hashCode()
indexOf(int ch)
indexOf(String str)
int length()
char[] toCharArray()
String toLowerCase()
String toUppercase()
String trim()