Bump actions/checkout from 3 to 4

.github/dependabot.yml

@@ -1,4 +1,4 @@
-# Configuration file of Github Dependabot
+# Configuration file of GitHub Dependabot
 
 version: 2
 updates:

.github/workflows/build.yml

@@ -1,4 +1,4 @@
-# Workflow file of Github Actions
+# Workflow file of GitHub Actions
 
 name: build
 
@@ -12,44 +12,31 @@ on:
       - master
 
 jobs:
-  build-on-jdk-8:
+  build:
     runs-on: ubuntu-latest
-    steps:
-      - name: Checkout scm
-        uses: actions/[email protected]
-      - name: Set up JDK 8
-        uses: actions/setup-java@v1
-        with:
-          java-version: 8
-      - name: Set up Codecov
-        run: pip install --user codecov
-      - name: Build with Maven
-        run: mvn clean install -DskipTests=true -Dmaven.javadoc.skip=true -B -V
-      - name: Test with Maven
-        run: mvn test -B
-      - name: Codecov
-        uses: codecov/[email protected]
-        with:
-          name: Codecov on jdk 8
-          fail_ci_if_error: true
+    strategy:
+      fail-fast: false
+      matrix:
+        java: [ 8, 11, 16, 17 ]
 
-  build-on-jdk-11:
-    runs-on: ubuntu-latest
     steps:
       - name: Checkout scm
-        uses: actions/[email protected]
-      - name: Set up JDK 11
-        uses: actions/setup-java@v1
+        uses: actions/checkout@v4
+
+      - name: Set up jdk
+        uses: actions/setup-java@v3
         with:
-          java-version: 11
-      - name: Set up Codecov
-        run: pip install --user codecov
+          distribution: 'zulu'
+          java-version: ${{ matrix.java }}
+
       - name: Build with Maven
         run: mvn clean install -DskipTests=true -Dmaven.javadoc.skip=true -B -V
+
       - name: Test with Maven
         run: mvn test -B
+
       - name: Codecov
-        uses: codecov/codecov-action@v1.2.1
+        uses: codecov/codecov-action@v3
         with:
-          name: Codecov on jdk 11
-          fail_ci_if_error: true
+          name: Codecov on jdk ${{ matrix.java }}
+          fail_ci_if_error: false

src/main/java/com/bestvike/Index.java

@@ -0,0 +1,99 @@
+package com.bestvike;
+
+import com.bestvike.linq.exception.ExceptionArgument;
+import com.bestvike.linq.exception.ThrowHelper;
+
+/**
+ * Represent a type can be used to index a collection either from the start or the end.
+ * <p>
+ * <pre>
+ * {@code
+ * List<Integer> list = Arrays.asList(1, 2, 3, 4, 5);
+ * Integer lastElement = Linq.of(list).elementAt(Index.fromEnd(1)); // lastElement = 5
+ * }
+ * </pre>
+ * <p>
+ * Created by 许崇雷 on 2023-05-31.
+ */
+public final class Index {
+    public static final Index Start = new Index(0);
+    public static final Index End = new Index(~0);
+    private final int value;
+
+    // The following private constructors mainly created for perf reason to avoid the checks
+    private Index(int value) {
+        this.value = value;
+    }
+
+    public Index(int value, boolean fromEnd) {
+        if (value < 0)
+            ThrowHelper.throwArgumentOutOfRangeException(ExceptionArgument.value);
+        if (fromEnd) {
+            this.value = ~value;
+        } else {
+            this.value = value;
+        }
+    }
+
+    public static Index fromStart(int value) {
+        if (value < 0)
+            ThrowHelper.throwArgumentOutOfRangeException(ExceptionArgument.value);
+        return new Index(value);
+    }
+
+    public static Index fromEnd(int value) {
+        if (value < 0)
+            ThrowHelper.throwArgumentOutOfRangeException(ExceptionArgument.value);
+        return new Index(~value);
+    }
+
+    public int getValue() {
+        if (this.value < 0)
+            return ~this.value;
+        else
+            return this.value;
+    }
+
+    public boolean isFromEnd() {
+        return this.value < 0;
+    }
+
+    public int getOffset(int length) {
+        int offset = this.value;
+        if (this.isFromEnd()) {
+            offset += length + 1;
+        }
+        return offset;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj instanceof Index) {
+            return this.value == ((Index) obj).value;
+        }
+        return false;
+    }
+
+    @Override
+    public int hashCode() {
+        return this.value;
+    }
+
+    @Override
+    @SuppressWarnings("MethodDoesntCallSuperMethod")
+    protected Index clone() {
+        return new Index(this.value);
+    }
+
+    @Override
+    public String toString() {
+        if (this.isFromEnd()) {
+            return this.toStringFromEnd();
+        }
+        return String.valueOf(this.value);
+    }
+
+    private String toStringFromEnd() {
+        return '^' + String.valueOf(this.getValue());
+    }
+}

src/main/java/com/bestvike/Range.java

@@ -0,0 +1,106 @@
+package com.bestvike;
+
+import com.bestvike.linq.exception.ExceptionArgument;
+import com.bestvike.linq.exception.ThrowHelper;
+
+/**
+ * Represent a range has start and end indexes.
+ * <p>
+ * <pre>
+ * {@code
+ * List<Integer> someArray = Arrays.asList(1, 2, 3, 4, 5);
+ * Integer[] subArray1 = Linq.of(someArray).take(Range.endAt(Index.fromStart(2))).toArray(Integer.class); // { 1, 2 }
+ * Integer[] subArray2 = Linq.of(someArray).take(Range.startAt(Index.fromStart(1))).toArray(Integer.class); // { 2, 3, 4, 5 }
+ * }
+ * </pre>
+ * <p>
+ * Created by 许崇雷 on 2023-05-31.
+ */
+public final class Range {
+    public static final Range All = new Range(Index.Start, Index.End);
+    private final Index start;
+    private final Index end;
+
+    public Range(Index start, Index end) {
+        if (start == null)
+            ThrowHelper.throwArgumentNullException(ExceptionArgument.start);
+        if (end == null)
+            ThrowHelper.throwArgumentNullException(ExceptionArgument.end);
+        this.start = start;
+        this.end = end;
+    }
+
+    public static Range startAt(Index start) {
+        return new Range(start, Index.End);
+    }
+
+    public static Range endAt(Index end) {
+        return new Range(Index.Start, end);
+    }
+
+    public Index getStart() {
+        return this.start;
+    }
+
+    public Index getEnd() {
+        return this.end;
+    }
+
+    public OffsetLength getOffsetAndLength(int length) {
+        int start;
+        Index startIndex = this.getStart();
+        if (startIndex.isFromEnd())
+            start = length - startIndex.getValue();
+        else
+            start = startIndex.getValue();
+
+        int end;
+        Index endIndex = this.getEnd();
+        if (endIndex.isFromEnd())
+            end = length - endIndex.getValue();
+        else
+            end = endIndex.getValue();
+
+        if (Integer.compareUnsigned(end, length) > 0 || Integer.compareUnsigned(start, end) > 0)
+            ThrowHelper.throwArgumentOutOfRangeException(ExceptionArgument.length);
+
+        return new OffsetLength(start, end - start);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj instanceof Range) {
+            Range r = (Range) obj;
+            return this.start.equals(r.start) && this.end.equals(r.end);
+        }
+        return false;
+    }
+
+    @Override
+    public int hashCode() {
+        int h1 = this.start.hashCode();
+        int h2 = this.end.hashCode();
+        return (h1 << 5) + h1 ^ h2;
+    }
+
+    @Override
+    @SuppressWarnings("MethodDoesntCallSuperMethod")
+    protected Range clone() {
+        return new Range(this.start, this.end);
+    }
+
+    @Override
+    public String toString() {
+        return this.start.toString() + ".." + this.end.toString();
+    }
+
+    public static final class OffsetLength {
+        public final int Offset;
+        public final int Length;
+
+        public OffsetLength(int offset, int length) {
+            this.Offset = offset;
+            this.Length = length;
+        }
+    }
+}