如何在不使用复杂代码结构的情况下串联Java中的字符串？

Question

I have the following java code:

String strTest = null;

for (AlternativeEntity alternativeEntity : msg.Guidance()
      .getAlternatives()) {

    strTest = strTest + alternativeEntity.getArrivalStation().getName() + ", ";

}

The output looks like this:

nullabc, xyz, oop, 

How can I solve this problem and very bad character format? It would be great if I can create output like this:

abc, xyz, oop

Answer 1

Initialize strTest as:

String strTest = "";

Also, remove the last comma ,

strTest=strTest.substring(0, strTest.length()-1);

Answer 2

You can use Guava 's Joiner#join(Iterable parts) . For example:

Joiner joiner = Joiner.on(", ").skipNulls();
String result = joiner.join(list);
System.out.println(result);

Here, all the elements of the list will be printed comma separated without any trailing commas. Also, all the null elements will be skipped.

More info:

• Strings Explained

Answer 3

Initialize your string to "":

 String strTest = "";

Alternatively, you should use a StringBuilder:

 StringBuilder builder = new StringBuilder();

 for (AlternativeEntity alternativeEntity : msg.Guidance()
  .getAlternatives()) {

     builder.append(alternativeEntity.getArrivalStation().getName()).append(", ");

 }

This will produce better performance.

Answer 4

Java provides StringBuilder class just for this purpose,its simple and easy to use..

    StringBuilder str = new StringBuilder("India ");

     //to append "Hi"
    str.append("Hi");

    // print the whole string
    System.out.println("The string is "+str)

the output will be : The string is India Hi

click here to know more about StringBuilder class

Answer 5

Replace String strTest = null; by String strTest = "";

Answer 6

Change

 String strTest = null;

to

String strTest = "";

Answer 7

why don't you use:

String strTest = "";

and at the end:

if(strTest.endsWith(", "))
   strTest = strTest.substring(0, strTest.length()-2);

Answer 8

Initialize String strTest="";

For skipping the last comma',' Use outside For loop:

strTest = strTest.substring(0,strTest.trim().length()-1);

Answer 9

String strTest = null;

for (AlternativeEntity alternativeEntity : msg.Guidance().getAlternatives()) {
  String name = alternativeEntity.getArrivalStation().getName();
  strTest = (strTest == null) ? name : strTest +  ", " + name;
}

If the list is long, you should use a StringBuilder rather than the String for strTest because the code above builds a fresh string on each iteration: far too much copying.