Java StringJoiner _Java新特性

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, 你可以通过传递诸如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

建设者	描述
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。如果分隔符为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带任何字符的StringJoiner。如果前缀, 定界符或后缀为null, 则抛出NullPointerException。

StringJoiner方法

方法	描述
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)	如果它不是空的, 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：

Rahul, Raju, Peter, Raheem

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); } }

【Java StringJoiner】输出：