Vanlig

String & formatering

int km = 360;
double kmPrHr = 57.8;
double hours = km / kmPrHr;
System.out.println("It takes about " + hours + " hours to drive "
                   + km + "km with " + kmPrHr + "km/hr average speed.");

// Result
It takes about 6.228373702422146 hours to drive 360km with 57.8km/hr average speed.

Formatert

int km = 360;
double kmPrHr = 57.8;
double hours = km / kmPrHr;
System.out.format("It takes about %.2f hours to drive %dkm" + 
                  "with %.1fkm/hr average speed.\n",
                  hours, km, kmPrHr);

// Result
It takes about 6.23 hours to drive 360km with 57.8km/hr average speed.

String & formatering

De vanligste formateringene

• String  %s
• int  %d
• double/float %f

Mer info ved googling: "String format java"

øverste resultat 'class Formatter'

String & formatering

Tabeller helt basic

int[] hoursWorked = {4, 5, 0, 4, 6, 2, 3};
String[] weekdays = {"Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"};

for (int i=0; i<weekdays.length; i++) {
    System.out.println(weekdays[i] + ": " + hoursWorked[i]);
}

// Result
Mon: 4
Tue: 5
Wed: 0
Thu: 4
Fri: 6
Sat: 2
Sun: 3

String & formatering

Tabeller litt bedre

int[] hoursWorked = {4, 5, 0, 4, 6, 2, 3};
String[] weekdays = {"Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"};

// Better ?

for (int i=0; i<weekdays.length; i++)
    System.out.print(weekdays[i] + " ");
System.out.println();
for (int i=0; i<hoursWorked.length; i++)
    System.out.print(" " + hoursWorked + " ");
System.out.println();

// Result
Mon Tue Wed Thu Fri Sat Sun 
 4  5  0  4  6  2  3 

String & formatering

Flere formateringsmuligheter

%-4.2f

'-'  betyr at det skal left-alignes

'4'  betyr at det skal være minst 4 plasser venstre for punktum

'.2'  betyr at det skal være minst 2 plasser etter punktum

'f'  betyr at dette er en float

String & formatering

Tabeller formatert

int[] hoursWorked = {4, 5, 0, 4, 6, 2, 3};
String[] weekdays = {"Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"};

// Better ?

for (int i=0; i<weekdays.length; i++)
    System.out.format("%3s ", weekdays[i]);
System.out.println();
for (int i=0; i<hoursWorked.length; i++)
    System.out.format("%3d ", hoursWorked[i]);
System.out.println();

// Result
Mon Tue Wed Thu Fri Sat Sun 
  4   5   0   4   6   2   3 

String & formatering

Tabeller med String

int[] hoursWorked = {4, 5, 0, 4, 6, 2, 3};
String[] weekdays = {"Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"};

// Even Better ?
String descriptionLine = "";
String workLine = "";
for (int i=0; i<weekdays.length; i++) {
    descriptionLine += String.format("%3s ", weekdays[i]);
    workLine += String.format("%3d ", hoursWorked[i]);
}
System.out.format("%s\n%s\n", descriptionLine, workLine);

// Result
Mon Tue Wed Thu Fri Sat Sun 
  4   5   0   4   6   2   3 

String & formatering

Vanlig

Metoder og returverdi

public void printArray() {
    int[] hoursWorked = {4, 5, 0, 4, 6, 2, 3};
    String[] weekdays = {"Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"};
    String descriptionLine = "";
    String workLine = "";
    for (int i=0; i<weekdays.length; 
        descriptionLine += String.format("%3s ", weekdays[
        workLine += String.format("%3d ", hoursWorked[i]);
    }
    System.out.format("%s\n%s\n", descriptionLine, workLine);
}

Litt videre

Metoder og returverdi

public String printArray() {
    int[] hoursWorked = {4, 5, 0, 4, 6, 2, 3};
    String[] weekdays = {"Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"};
    String descriptionLine = "";
    String workLine = "";
    for (int i=0; i<weekdays.length; 
        descriptionLine += String.format("%3s ", weekdays[
        workLine += String.format("%3d ", hoursWorked[i]);
    }
    return String.format("%s\n%s\n", descriptionLine, workLine);
}

public void execute() {
    String arrayPrint = printArray();
    System.out.print(arrayPrint);
}

// result same as before

Mon Tue Wed Thu Fri Sat Sun 
  4   5   0   4   6   2   3

Live eksempel

Metoder og returverdi

/**
 * Generates the graph of tree from this node forward.
 *
 * @return the String representing recursive version of graph
 */
protected String generateGraph() {	
    String result = String.format("%c", this.c);
    if (childrenCount == 1) {
	result += String.format("%s", onlyChild.generateGraph());
    }
    else {
	int counter = 0;
	for (int i=0; (i < children.length && counter < childrenCount); i++) {
            if (children[i] != null) {
		counter++;
		result += String.format("(%s)", children[i].generateGraph());
	    }
	}
    }
    return result;
}

// Example result

internet (internet)
interview (inter(net)(view))
internally (inter(n(ally)(et))(view))
algorithm (algorithm)
all (al(gorithm)(l))
web (web)
world (w(eb)(orld))

Fordeler

• Formatert String +
• Metode som returnerer denne = 
• En fin tekst å benytte

• Kan printes til skjerm eller til fil
• 1 metode < flere muligheter

I/O, mer om O

Bruker bestemmer

private static void executeCommand(String cmd) throws Exception {
    String[] splitCmd = cmd.split(" ");
    switch (splitCmd[0].toLowerCase()) {
        case "export":
            if (splitCmd.length < 3) {
    	        print("Not enough arguments for 'export', see usage\n");
    	        return;
            }
            String outfilename = splitCmd[2];
            PrintWriter out = new PrintWriter(new File(outfilename));
            switch (splitCmd[1].toLowerCase()) {
                case "print": case "p":
    	            out.write(printArray());
    	            break;
                case "help": case "h":
    	            out.write(usage());
    	            break;
                }
            out.close();
            break;
        case "print": case "p":
            print(printArray());
            break;
        case "help": case "h":
            print(usage());
            break;
    }
}

I/O, mer om O