Java在java.util包中添加了一个新的最终类StringJoiner。它用于构造由定界符分隔的字符序列。现在，您可以通过传递诸如comma(，)，hyphen(-)等分隔符来创建字符串。您还可以将前缀和后缀传递给char序列。
| Constructor | Description |
|---|---|
| Public StringJoiner(CharSequence delimiter) | It constructs a StringJoiner with no characters in it, with no prefix or suffix, and a copy of the supplied delimiter. It throws NullPointerException if delimiter is null. |
| Public StringJoiner(CharSequence delimiter,CharSequence prefix,CharSequence suffix) | It constructs a StringJoiner with no characters in it using copies of the supplied prefix, delimiter and suffix. It throws NullPointerException if prefix, delimiter, or suffix is null. |
| Method | Description |
|---|---|
| Public StringJoiner add(CharSequence newElement) | It adds a copy of the given CharSequence value as the next element of the StringJoiner value. If newElement is null,”null” is added. |
| Public StringJoiner merge(StringJoiner other) | It adds the contents of the given StringJoiner without prefix and suffix as the next element if it is non-empty. If the given StringJoiner is empty, the call has no effect. |
| Public int length() | It returns the length of the String representation of this StringJoiner. |
| Public StringJoiner setEmptyValue(CharSequence emptyValue) | It sets the sequence of characters to be used when determining the string representation of this StringJoiner and no elements have been added yet, that is, when it is empty. |
// importing StringJoiner class
import java.util.StringJoiner;
public class StringJoinerExample {
public static void main(String[] args) {
StringJoiner joinNames = new StringJoiner(",");// passing comma(,) as delimiter
// Adding values to StringJoiner
joinNames.add("Rahul");
joinNames.add("Raju");
joinNames.add("Peter");
joinNames.add("Raheem");
System.out.println(joinNames);
}
}
输出：
Rahul,Raju,Peter,Raheem
// importing StringJoiner class
import java.util.StringJoiner;
public class StringJoinerExample {
public static void main(String[] args) {
StringJoiner joinNames = new StringJoiner(",", "[", "]");// passing comma(,) and square-brackets as delimiter
// Adding values to StringJoiner
joinNames.add("Rahul");
joinNames.add("Raju");
joinNames.add("Peter");
joinNames.add("Raheem");
System.out.println(joinNames);
}
}
输出：
[Rahul,Raju,Peter,Raheem]
merge()方法合并两个StringJoiner对象，但不包括第二个StringJoiner对象的前缀和后缀。
// importing StringJoiner class
import java.util.StringJoiner;
public class StringJoinerExample {
public static void main(String[] args) {
StringJoiner joinNames = new StringJoiner(",", "[", "]");// passing comma(,) and square-brackets as delimiter
// Adding values to StringJoiner
joinNames.add("Rahul");
joinNames.add("Raju");
// Creating StringJoiner with :(colon) delimiter
StringJoiner joinNames2 = new StringJoiner(":", "[", "]");// passing colon(:) and square-brackets as delimiter
// Adding values to StringJoiner
joinNames2.add("Peter");
joinNames2.add("Raheem");
// Merging two StringJoiner
StringJoiner merge = joinNames.merge(joinNames2);
System.out.println(merge);
}
}
输出：
[Rahul,Raju,Peter:Raheem]
// importing StringJoiner class
import java.util.StringJoiner;
public class StringJoinerExample {
public static void main(String[] args) {
StringJoiner joinNames = new StringJoiner(",");// passing comma(,) as delimiter
// Prints nothing because it is empty
System.out.println(joinNames);
// We can set default empty value.
joinNames.setEmptyValue("It is empty");
System.out.println(joinNames);
// Adding values to StringJoiner
joinNames.add("Rahul");
joinNames.add("Raju");
System.out.println(joinNames);
// Returns length of StringJoiner
int length = joinNames.length();
System.out.println("Length: "+length);
// Returns StringJoiner as String type
String str = joinNames.toString();
System.out.println(str);
// Now, we can apply String methods on it
char ch = str.charAt(3);
System.out.println("Character at index 3: "+ch);
// Adding one more element
joinNames.add("Sorabh");
System.out.println(joinNames);
// Returns length
int newLength = joinNames.length();
System.out.println("New Length: "+newLength);
}
}
输出：
It is empty
Rahul,Raju
Length: 10
Rahul,Raju
Character at index 3: u
Rahul,Raju,Sorabh
New Length: 17
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