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[codeInsight] IDEA-219640 Inspection to detect some pointless String.substring

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IDEA didn't use to report pointless String.substring invocations for
cases when only one character in the string is extracted. In such cases
it makes more sense to use the String#charAt method because it is
allocation free.

IDEA didn't use to suggest to refactor for the code when String.substring
selects a single character and is followed by the equals method(e.g.
args[0].substring(0, 1).equals("_")) to more readable version e.g.
args[0].charAt(0) == '_'.

This patch adds such refactorings to both of the cases. It also adds
the possiblity to handle expressions like "i+1" and "i+2" to
com.siyeh.ig.psiutils.ExpressionUtils#isDifference.

Signed-off-by: Nikita Eshkeev <nikita.eshkeev@jetbrains.com>

GitOrigin-RevId: 6d179c7c9c605f08b4d4468712f8468fd68045a1
This commit is contained in:
Nikita Eshkeev
2020-04-14 10:09:01 +03:00
committed by intellij-monorepo-bot
parent 72259e1a5b
commit 7b6e636c13
7 changed files with 253 additions and 11 deletions
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2
java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantStringOperation/afterSubstringInAppend.java
View File

@@ -2,6 +2,6 @@
class Foo {
public static void main(String[] args) {
StringBuilder sb = new StringBuilder();
sb.append(args[0], 3, 4);
sb.append(args[0], 2, 4);
}
}

37
java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantStringOperation/afterSubstringOneCharInAppend.java Normal file
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@@ -0,0 +1,37 @@
// "Fix all 'Redundant String operation' problems in file" "true"
class Foo {
public static void main(String[] args) {
StringBuilder sb = new StringBuilder();
int i = Integer.parseInt(args[4]);
sb.append(args[0].charAt(0));
sb.append(args[0].charAt(2));
sb.append(args[0].charAt(i));
sb.append(args[0].charAt(i + 2));
sb.append(args[0].charAt(2 + i));
sb.append(args[0].charAt(i + 2));
sb.append(args[0].charAt(2 + i));
sb.append(args[0].substring(2 + i, 4 + i));
sb.append(args[0].substring(i + 2, i + 4));
String s1 = "xxx" + args[0].substring(3, 5);
String s2 = "xxx" + args[0].charAt(3);
String s3 = args[0].charAt(2) + "xxx";
boolean value = args[0].charAt(4) == '_';
if(args[0].charAt(4) == '_') { }
if(args[0].charAt(4) != '_') { }
if(args[0].charAt(4) == '_') { }
if(args[0].charAt(4) != '_') { }
System.out.print(args[0].charAt(2));
System.out.println(args[0].charAt(2));
System.out.print(args[0].substring(2, 4));
System.out.println(args[0].substring(2, 4));
}
}

2
java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantStringOperation/beforeSubstringInAppend.java
View File

@@ -2,6 +2,6 @@
class Foo {
public static void main(String[] args) {
StringBuilder sb = new StringBuilder();
sb.append(args[0].subs<caret>tring(3, 4));
sb.append(args[0].subs<caret>tring(2, 4));
}
}

37
java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/redundantStringOperation/beforeSubstringOneCharInAppend.java Normal file
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@@ -0,0 +1,37 @@
// "Fix all 'Redundant String operation' problems in file" "true"
class Foo {
public static void main(String[] args) {
StringBuilder sb = new StringBuilder();
int i = Integer.parseInt(args[4]);
sb.append(args[0].sub<caret>string(0, 1));
sb.append(args[0].substring(2, 3));
sb.append(args[0].substring(i, i + 1));
sb.append(args[0].substring(i + 2, i + 3));
sb.append(args[0].substring(2 + i, i + 3));
sb.append(args[0].substring(i + 2, 3 + i));
sb.append(args[0].substring(2 + i, 3 + i));
sb.append(args[0].substring(2 + i, 4 + i));
sb.append(args[0].substring(i + 2, i + 4));
String s1 = "xxx" + args[0].substring(3, 5);
String s2 = "xxx" + args[0].substring(3, 4);
String s3 = args[0].substring(2, 3) + "xxx";
boolean value = args[0].substring(4, 5).equals("_");
if(args[0].substring(4, 5).equals("_")) { }
if(!args[0].substring(4, 5).equals("_")) { }
if(!!args[0].substring(4, 5).equals("_")) { }
if(!!!!!args[0].substring(4, 5).equals("_")) { }
System.out.print(args[0].substring(2, 3));
System.out.println(args[0].substring(2, 3));
System.out.print(args[0].substring(2, 4));
System.out.println(args[0].substring(2, 4));
}
}