How to create a String in Java by adding char by char. I have to do it like this, because i have to add a "," between al letters. I tried it like this, but it had not worked.
String t;
int l = t.length();
char[] a;
a = new char[l];
String rel = ",";
String ret = null;
for (int i = 0; i<l; i++){
a[i] = new Character(t.charAt(0));
}
for (int v = 0; v<l; v--){
ret += a[v];
ret += rel;
}
If you use empty strings instead of null and initialize it then it works.
String t = "foobarbaz";
int l = t.length();
char[] a;
a = new char[l];
String rel = ",";
String ret = "";
for (int i = 0; i<l; i++){
a[i] = t.charAt(i);
}
for (int v = 0; v<l; v++){
ret += a[v];
ret += rel;
}
System.out.println(ret);
You don't need to do it so complicated, and you should explicitly use StringBuilder
for such string operations:
String s = "abcdefg";
StringBuilder builder = new StringBuilder();
for (char c : s.toCharArray()) {
builder.append(c).append(",");
}
// Alternatively, you can do it in this way
for (String symbol : s.split("")) {
builder.append(symbol).append(",");
}
System.out.println(builder.toString());
// Java 8 (the result string doesn't have a comma at the end)
String collect = Arrays.stream(s.split("")).collect(Collectors.joining(","));
// Java8 StringJoiner
StringJoiner sj = new StringJoiner(",");
// StringJoiner sj = new StringJoiner(",", "", ",");
for (String str : s.split("")) {
sj.add(str);
}
I've put the errors in your code in comments.
String t;
int l = t.length();
char[] a;
a = new char[l];
String rel = ",";
String ret = null; //you initialize ret to null, it should be "";
for (int i = 0; i<l; i++){
//you always set it to the character at position 0, you should do t.charAt(i)
//you don't need to use the wrapper class just t.charAt(i) will be fine.
a[i] = new Character(t.charAt(0));
}
for (int v = 0; v<l; v--){//you decrement v instead of incrementing it, this will lead to exceptions
ret += a[v];
ret += rel;//you always add the delimiter, note that this will lead to a trailing delimiter at the end
}
You might want to try a StringBuilder. It's a lot more efficient than using string concatenation. Using the array a is also not really necessary. Have a look at this implementation.
String t = "Test";
StringBuilder builder = new StringBuilder();
if(t.length() > 0){
builder.append(t.charAt(0));
for(int i=1;i<t.length();i++){
builder.append(",");
builder.append(t.charAt(i));
}
}
System.out.println(builder.toString());
Take a look at this:
//Word to be delimited by commas
String t = "ThisIsATest";
//get length of word.
int l = t.length(); //4
char[] a;
a = new char[l];
// we will set this to a comma below inside the loop
String rel = "";
//set ret to empty string instead of null otherwise the word "null" gets put at the front of your return string
String ret = "";
for (int i = 0; i<l; i++){
//you had 0 instead of 'i' as the parameter of t.charAt. You need to iterate through the elements of the string as well
a[i] = new Character(t.charAt(i));
}
for (int v = 0; v<l; v++){
/*set rel to empty string so that you can add it BEFORE the first element of the array and then afterwards change it to a comma
this prevents you from having an extra comma at the end of your list. */
ret += rel;
ret += a[v];
rel = ",";
}
System.out.println(ret);
String text = "mydata";
char[] arrayText = text.toCharArray();
char[] arrayNew = new char[arrayText.length*2];
for(int i = 0, j = 0; i < arrayText.length; i++, j+=2){
arrayNew[j] = arrayText[i];
arrayNew[j+1] = ',';
}
String stringArray = new String(arrayNew);
System.out.println(stringArray);
Results
m,y,d,a,t,a,
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.