Java StringJoiner
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。还可以将前缀和后缀传递给char序列。
StringJoiner构造函数
| 构造函数 |
说明 |
| Public StringJoiner(CharSequence delimiter) |
它构造一个不带任何字符，没有前缀或后缀的StringJoiner，以及提供的定界符的副本。如果定界符为null，则抛出NullPointerException。 |
| Public StringJoiner(CharSequence delimiter,CharSequence prefix,CharSequence suffix) |
它使用提供的前缀，定界符和后缀的副本构造一个不包含任何字符的StringJoiner。如果前缀，定界符或后缀为null，则会抛出NullPointerException。 |
StringJoiner方法
| 方法 |
说明 |
| Public StringJoiner add(CharSequence newElement) |
它将给定CharSequence值的副本添加为StringJoiner值的下一个元素。如果newElement为null，则添加" null"。 |
| Public StringJoiner merge(StringJoiner other) |
如果非空，它将添加不带前缀和后缀的给定StringJoiner的内容作为下一个元素。如果给定的StringJoiner为空，则该调用无效。 |
| Public int length() |
它返回此StringJoiner的String表示形式的长度。 |
| Public StringJoiner setEmptyValue(CharSequence emptyValue) |
它设置确定此StringJoiner的字符串表示形式时要使用的字符序列，并且尚未添加任何元素，即当它为空时。 |
Java StringJoiner示例
// 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:
Java StringJoiner示例: 添加前缀和后缀
// 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");
joinNames.add("Peter");
joinNames.add("Raheem");
System.out.println(joinNames);
}
}
输出:
[Rahul,Raju,Peter,Raheem]
StringJoiner示例: 合并两个StringJoiner
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]
StringJoiner示例: StringJoiner方法
// 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
