String Variablen und Konkatenation

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Ein wichtiges Konzept in der Programmierung sind Variablen. Eine Variable ist ein Platzhalter für einen Wert, der sich im laufe eines Programms ändern kann. Wir beschäftigen uns zuerst mit Variablen, die Text speichern. Diese nennt man String-Variablen oder Strings.

Eine Variable kann folgendermaßen deklariert, also erstmalig beschrieben werden:

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String superHero;
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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Dabei ist String der Variablentyp, in unserem Fall ein Text, und superHero der Variablenname. Dieser ist (bis auf einige Einschränkungen bzgl. Zahlen und Sonderzeichen) frei wählbar. Um einer Variable einen Wert zuzuweisen, kann man den Zuweisungsoperator = verwenden:

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superHero = "Iron Man";
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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Häufig werden diese beiden Schritte zusammengefasst zu einer Zeile:

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String superHero = "Iron Man";
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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Anstatt nun den immer gleichen Text auf der Konsole auszugeben, können wir die Variable als Platzhalter verwenden:

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String superHero = "Iron Man";
System.out.println("Der Superheld ist " + superHero);
superHero = "Thor";
System.out.println("Der Superheld ist jetzt " + superHero);
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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+ ist der Verkettungs-Operator, der unterschiedliche Strings zu einem einzelnen zusammenfügt. Man spricht auch von Konkatenation (Verkettung).

Das Ergebnis des obigen Programmschnipsels wäre dann:

Der Superheld ist Iron Man
Der Superheld ist jetzt Thor

Deine Aufgabe ist es nun, zwei String-Variablen namens firstName und lastName zu deklarieren und ihnen Werte zuzuweisen. Anschließend soll auf der Konsole folgender Text ausgegeben werden:

Guten Tag, VORNAME NACHNAME!

Hierbei soll VORNAME und NACHNAME jeweils den Werten der Variablen entsprechen.

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Überprüfe anschließend die Konsolenausgabe, ob auch wirklich exakt der gewünschte Text ausgegeben wurde.

Häufige Fehlerquellen

Du hast ein Semikolon vergessen
Du hast ein Gänsefüßchen zu viel oder zu wenig
Du hast das Leerzeichen zwischen den zwei Variablen vergessen
Du hast zwar die Variablen deklariert, ihnen aber keine Werte zugewiesen

Lösungsvorschlag

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public class Example {
    public static void main(String[] args) {
        String firstName = "Peter";
        String lastName = "Lustig";
        System.out.println("Guten Tag, " + firstName + " " + lastName + "!");
    }
}
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
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