问题

I was wondering if someone can show me how to use the format method for Java Strings. For instance If I want the width of all my output to be the same

For instance, Suppose I always want my output to be the same

Name =              Bob
Age =               27
Occupation =        Student
Status =            Single

In this example, all the output are neatly formatted under each other; How would I accomplish this with the format method.

回答1:

EDIT: This is an extremely primitive answer but I can't delete it because it was accepted. See the answers below for a better solution though

Why not just generate a whitespace string dynamically to insert into the statement.

So if you want them all to start on the 50th character...

String key = "Name =";
String space = "";
for(int i; i<(50-key.length); i++)
{space = space + " ";}
String value = "Bob\n";
System.out.println(key+space+value);

Put all of that in a loop and initialize/set the "key" and "value" variables before each iteration and you're golden. I would also use the StringBuilder class too which is more efficient.

回答2:

System.out.println(String.format("%-20s= %s" , "label", "content" ));

Where %s is a placeholder for you string.
The '-' makes the result left-justified.
20 is the width of the first string

The output looks like this:

label               = content

As a reference I recommend Javadoc on formatter syntax

回答3:

If you want a minimum of 4 characters, for instance,

System.out.println(String.format("%4d", 5));
// Results in "   5", minimum of 4 characters

回答4:

To answer your updated question you can do

String[] lines = ("Name =              Bob\n" +
        "Age =               27\n" +
        "Occupation =        Student\n" +
        "Status =            Single").split("\n");

for (String line : lines) {
    String[] parts = line.split(" = +");
    System.out.printf("%-19s %s%n", parts[0] + " =", parts[1]);
}

prints

Name =              Bob
Age =               27
Occupation =        Student
Status =            Single

回答5:

@Override
public String toString()
{
  return String.format("%15s /n %15d /n %15s /n   %15s",name,age,Occupation,status);
}

回答6:

For decimal values you can use DecimalFormat

import java.text.*;

public class DecimalFormatDemo {

   static public void customFormat(String pattern, double value ) {
      DecimalFormat myFormatter = new DecimalFormat(pattern);
      String output = myFormatter.format(value);
      System.out.println(value + "  " + pattern + "  " + output);
   }

   static public void main(String[] args) {

      customFormat("###,###.###", 123456.789);
      customFormat("###.##", 123456.789);
      customFormat("000000.000", 123.78);
      customFormat("$###,###.###", 12345.67);  
   }
}

and output will be:

123456.789  ###,###.###   123,456.789
123456.789  ###.##        123456.79
123.78      000000.000    000123.780
12345.67    $###,###.###  $12,345.67

For more details look here:

http://docs.oracle.com/javase/tutorial/java/data/numberformat.html

来源：https://stackoverflow.com/questions/4418308/java-output-formatting-for-strings

标签

java

formatting

Java output formatting for Strings

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