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e21cbe82a9
Where possible update Java documentation links to Java 11. Additionally update some other links to use HTTPS.
48 lines
1.5 KiB
XML
48 lines
1.5 KiB
XML
<!DOCTYPE qhelp PUBLIC
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"-//Semmle//qhelp//EN"
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"qhelp.dtd">
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<qhelp>
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<overview>
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<p>The <code>String</code> class is immutable, which means that there is
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no way to change the string that it represents. Consequently, there is rarely a
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need to copy a <code>String</code> object or construct a new instance based on
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an existing string, for example by writing something like <code>String hello =
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new String("hello")</code>. Furthermore, this practice is not memory efficient.</p>
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</overview>
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<recommendation>
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<p>The copied string is functionally indistinguishable from the argument that
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was passed into the <code>String</code> constructor, so you can simply omit the constructor call and
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use the argument passed into it directly. Unless an explicit copy of the argument string is needed,
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this is a safe transformation.</p>
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</recommendation>
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<example>
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<p>The following example shows three cases of copying a string using the <code>String</code>
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constructor, which is inefficient. In each case, simply removing the constructor call
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<code>new String</code> and leaving the argument results in better code and less
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memory churn.</p>
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<sample src="NewStringString.java" />
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</example>
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<references>
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<li>
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J. Bloch, <em>Effective Java (second edition)</em>,
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Item 5.
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Addison-Wesley, 2008.
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</li>
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<li>
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Java API Specification:
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<a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/String.html#%3Cinit%3E(java.lang.String)">String(String)</a>.
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</li>
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</references>
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</qhelp>
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