What are connecting characters in Java while defining identifiers?

As per Java specification, identifiers must start with a letter, $, or a connecting character such as underscore ( _ ).

Following table summarizes the characters that come under connector category.

Unicode number	Name	Symbol
U+005F	LOW LINE	_
U+203F	UNDERTIE	‿
U+2040	CHARACTER TIE	⁀
U+2054	INVERTED UNDERTIE	⁔
U+FE33	PRESENTATION FORM FOR VERTICAL LOW LINE	︳
U+FE34	PRESENTATION FORM FOR VERTICAL WAVY LOW LINE	︴
U+FE4D	DASHED LOW LINE	﹍
U+FE4E	CENTRELINE LOW LINE	﹎
U+FE4F	WAVY LOW LINE	﹏
U+FF3F	FULLWIDTH LOW LINE	＿

App.java

package com.sample.app;

public class App {

 public static void main(String args[]) {
  int _ = 10, ‿ = 20, ⁀ = 30, ⁔ = 40, ︳ = 50, ︴ = 60, ﹍ = 70;

  System.out.println("_ : " + _);
  System.out.println("‿ : " + ‿);
  System.out.println("⁀ : " + ⁀);
  System.out.println("⁔ : " + ⁔);
  System.out.println("︳ : " + ︳);
  System.out.println("︴ : " + ︴);
  System.out.println("﹍ : " + ﹍);
 }

}

Output

_ : 10
‿ : 20
⁀ : 30
⁔ : 40
︳ : 50
︴ : 60
﹍ : 70

Apart from the above table, there are many characters that you can use as first character while defining identifier in Java. Use the method ‘Character.isJavaIdentifierStart’ to check whether you can use given character as first character or not while defining an identifier.

App.java

package com.sample.app;

public class App {

    public static void main(String args[]) {
        for (int i = Character.MIN_CODE_POINT; i < Character.MAX_CODE_POINT; i++) {
            if (Character.isJavaIdentifierStart(i)) {
                System.out.print((char) +i + " ");
            }
        }
    }

}

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