isjavaid.html
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<TITLE>Determining If a String Is a Legal Java Identifier
(Java Developers Almanac Example)
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<h3>
e81.
Determining If a String Is a Legal Java Identifier</h3>
Briefly, a valid Java identifier must start with a Unicode letter,
underscore, or dollar sign (<code>$</code>). The other characters, if any, can
be a Unicode letter, underscore, dollar sign, or digit.
<P> For more details, see
<a href="http://java.sun.com/docs/books/jls/second_edition/html/lexical.doc.html"><font size="-1">http://java.sun.com/docs/books/jls/second_edition/html/lexical.doc.html</font></a>.
<pre>
// Returns true if s is a legal Java identifier.
public static boolean isJavaIdentifier(String s) {
if (s.length() == 0 || !Character.isJavaIdentifierStart(s.charAt(0))) {
return false;
}
for (int i=1; i<s.length(); i++) {
if (!Character.isJavaIdentifierPart(s.charAt(i))) {
return false;
}
}
return true;
}
</pre>
<pre>
// Some examples
boolean b = isJavaIdentifier(<font color="#0066ff"><i>"my_var"</i></font>); // true
b = isJavaIdentifier(<font color="#0066ff"><i>"my_var.1"</i></font>); // false
b = isJavaIdentifier(<font color="#0066ff"><i>"$my_var"</i></font>); // true
b = isJavaIdentifier(<font color="#0066ff"><i>"\u0391var"</i></font>); // true
b = isJavaIdentifier(<font color="#0066ff"><i>"_"</i></font>); // true
b = isJavaIdentifier(<font color="#0066ff"><i>"$"</i></font>); // true
b = isJavaIdentifier(<font color="#0066ff"><i>"1$my_var"</i></font>); // false
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Related Examples
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e70. <a class="eglink" href="CreateUsingStringBuffer.html?l=rel">
Constructing a String
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e71. <a class="eglink" href="CompareStr.html?l=rel">
Comparing Strings
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e72. <a class="eglink" href="HasSubstr.html?l=rel">
Determining If a String Contains a Substring
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e73. <a class="eglink" href="GetSubstring.html?l=rel">
Getting a Substring from a String
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e74. <a class="eglink" href="SearchString.html?l=rel">
Searching a String for a Character or a Substring
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e75. <a class="eglink" href="ReplaceChar.html?l=rel">
Replacing Characters in a String
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e76. <a class="eglink" href="ReplaceString.html?l=rel">
Replacing Substrings in a String
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e77. <a class="eglink" href="UpperLower.html?l=rel">
Converting a String to Upper or Lower Case
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e78. <a class="eglink" href="PrimType2Str.html?l=rel">
Converting a Primitive Type Value to a String
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e79. <a class="eglink" href="UnicodeToUTF8.html?l=rel">
Converting Between Unicode and UTF-8
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e80. <a class="eglink" href="FindUnicodeBlock.html?l=rel">
Determining a Character's Unicode Block
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See also:
<a class="eglink" href="/egs/java.lang/pkg.html?l=rel#Arrays">
Arrays
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<a class="eglink" href="/egs/java.lang/pkg.html?l=rel#Assertions">
Assertions
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Classes
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<a class="eglink" href="/egs/java.lang/pkg.html?l=rel#Commands">
Commands
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<a class="eglink" href="/egs/java.lang/pkg.html?l=rel#Numbers">
Numbers
</a>
<a class="eglink" href="/egs/java.lang/pkg.html?l=rel#Objects">
Objects
</a>
<a class="eglink" href="/egs/java.lang/pkg.html?l=rel#System%20Properties">
System Properties
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<a class="eglink" href="/egs/java.lang/pkg.html?l=rel#Threads">
Threads
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