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How to remove the last line of characters in java

I want to remove the comma in the last data.

Example:

I have a code:

StringBuilder temp = new StringBuilder();

for (int i=0; i<allLines.size(); i++){
     StringBuilder temp2 = new StringBuilder();

     String[] abc = line.split("\t");

     temp2.append("{");
     temp2.append("id: \""+abc[0]+"\",");
     temp2.append("name: \""+abc[1]+"\",");
     temp2.append("},");

     temp.append(temp2.toString()); 

}

System.out.println("result : "+temp.toString());

Code and result:

{id: "1", name: "Jhames"},{id: "2", name: "Richard"},

but I want the result:

{id: "1", name: "Jhames"},{id: "2", name: "Richard"}
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6 answers


Just use the new java 8 StringJoiner ! (And other great Java methods)

Example:

StringJoiner joiner = new StringJoiner(",");
joiner.add("foo");
joiner.add("bar");
joiner.add("baz");
String joined = joiner.toString(); // "foo,bar,baz"


It also supports streams in the form Collectors.joining(",")

Complete example:

public static void main(String[] args) {

    String input = "1\tJames\n2\tRichard";
    String output =  Arrays.stream(input.split("\n"))
                        .map( i -> String.format("{ id: \"%s\", name: \"%s\" }", i.split("\t")))
                        .collect(Collectors.joining(","));

    //prints: { id: "1", name: "James" },{ id: "2", name: "Richard" }       
    System.out.println(output);

}
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You can avoid adding it in the first place:



for (int i=0; i<allLines.size(); i++){
     StringBuilder temp2 = new StringBuilder();

     String[] abc = line.split("\t");

     temp2.append("{");
     temp2.append("id: \""+abc[0]+"\",");
     temp2.append("name: \""+abc[1]+"\",");
     temp2.append("}");
     if (i<allLines.size()-1)
         temp2.append(",");
     temp.append(temp2.toString()); 

}
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Alternatively add this after the for loop

    temp.setLength(temp.length() - 1);

which doesn't require constant checking of the index in your code

+2


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You can use the deleteCharAt () method.

 StringBuilder s = new StringBuilder("{id: \"1\", name: \"Jhames\"},{id: \"2\", name: \"Richard\"},");
 System.out.println(s.deleteCharAt(s.lastIndexOf(",")));
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No Java 8 solution:

StringBuilder temp = new StringBuilder();
adder(temp, allLines.get(0));

for (int i=1; i<allLines.size(); i++){
     temp.append(",");
     adder(temp, allLines.get(i));
}
System.out.println("result : "+temp.toString());

private static void adder(StringBuilder temp,String line){
    String[] abc = line.split("\t");
    temp.append("{id: \"");
    temp.append(abc[0]);
    temp.append("\",");
    temp.append("name: \"");
    temp.append(abc[1]);
    temp.append("\"}");
}
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First of all you don't need two StringBuilders, so instead of

StringBuilder sb1 = ..
for(..){
    StringBuilder sb2 = ...
    //fill sb2
    sb1.append(sb2);
}

you must use

StringBuilder sb1 = ..
for(..){
    //add all you want to sb1
    sb1.append(..)
    sb1.append(..)
}

The next thing you never want to do

sb.appent("foo" + x + "bar");

since it is similar

sb.append(new StringBuilder("foo").append(x).append("bar").toString())

which is very inefficient because:

  • you create a separate StringBuilder every time you do this
  • this new StringBuilder needs an unnecessary method call toString

    , which is to copy all the characters into a new String, which will later be copied to the builder, instead of calling append(StringBuilder)

    and copy its characters directly.

So instead of sb.appent("foo" + x + "bar");

always write

sb.appent("foo").append(x).append("bar");

Now, back to your main problem. Since your code does not have a variable declaration line

, I will assume that

String[] abc = line.split("\t");

you mean

String[] abc = allLines.get(i).split("\t");

So your code might look like

StringBuilder temp = new StringBuilder();

for (int i = 0; i < allLines.size(); i++) {

    String[] abc = allLines.get(i).split("\t");

    temp.append("{id: \"").append(abc[0]).append("\", ");
    temp.append("name: \"").append(abc[1]).append("\"}");
    if (i < allLines.size() - 1)
        temp.append(", ");
}

System.out.println("result : " + temp.toString());
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