use more high-level methods to copy arrays instead of low-level cryptic System.arraycopy()

GitOrigin-RevId: 16b9869eae4200f4ff24c4535d7f33d8e6847b4c

src/org/jetbrains/java/decompiler/struct/gen/MethodDescriptor.java

@@ -68,8 +68,7 @@ public final class MethodDescriptor {
 
     VarType[] newParams;
     if (params.length > 0) {
-      newParams = new VarType[params.length];
+      newParams = params.clone();
-      System.arraycopy(params, 0, newParams, 0, params.length);
       for (int i = 0; i < params.length; i++) {
         VarType substitute = buildNewType(params[i], builder);
         if (substitute != null) {

src/org/jetbrains/java/decompiler/util/FastFixedSetFactory.java

@@ -1,10 +1,7 @@
 // Copyright 2000-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package org.jetbrains.java.decompiler.util;
 
-import java.util.Collection;
+import java.util.*;
-import java.util.HashSet;
-import java.util.Iterator;
-import java.util.Set;
 
 public class FastFixedSetFactory<E> {
 
@@ -66,8 +63,7 @@ public class FastFixedSetFactory<E> {
       FastFixedSet<E> copy = new FastFixedSet<>(factory);
 
       int arrlength = data.length;
-      int[] cpdata = new int[arrlength];
+      int[] cpdata = Arrays.copyOf(data, arrlength);
-      System.arraycopy(data, 0, cpdata, 0, arrlength);
       copy.setData(cpdata);
 
       return copy;

src/org/jetbrains/java/decompiler/util/FastSparseSetFactory.java

@@ -1,10 +1,7 @@
 // Copyright 2000-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package org.jetbrains.java.decompiler.util;
 
-import java.util.Collection;
+import java.util.*;
-import java.util.HashSet;
-import java.util.Iterator;
-import java.util.Set;
 
 public class FastSparseSetFactory<E> {
 
@@ -97,15 +94,7 @@ public class FastSparseSetFactory<E> {
     }
 
     public FastSparseSet<E> getCopy() {
-
+      return new FastSparseSet<>(factory, data.clone(), next.clone());
-      int arrlength = data.length;
-      int[] cpdata = new int[arrlength];
-      int[] cpnext = new int[arrlength];
-
-      System.arraycopy(data, 0, cpdata, 0, arrlength);
-      System.arraycopy(next, 0, cpnext, 0, arrlength);
-
-      return new FastSparseSet<>(factory, cpdata, cpnext);
     }
 
     private int[] ensureCapacity(int index) {
@@ -119,15 +108,10 @@ public class FastSparseSetFactory<E> {
         newlength *= 2;
       }
 
-      int[] newdata = new int[newlength];
+      data = Arrays.copyOf(data, newlength);
-      System.arraycopy(data, 0, newdata, 0, data.length);
+      next = Arrays.copyOf(next, newlength);
-      data = newdata;
 
-      int[] newnext = new int[newlength];
+      return data;
-      System.arraycopy(next, 0, newnext, 0, next.length);
-      next = newnext;
-
-      return newdata;
     }
 
     public void add(E element) {

src/org/jetbrains/java/decompiler/util/SFormsFastMapDirect.java

@@ -5,6 +5,7 @@ import org.jetbrains.java.decompiler.modules.decompiler.exps.VarExprent;
 import org.jetbrains.java.decompiler.util.FastSparseSetFactory.FastSparseSet;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import java.util.Map.Entry;
 import java.util.Set;
@@ -66,9 +67,7 @@ public class SFormsFastMapDirect {
         int[] arrnext = next[i];
 
         @SuppressWarnings("unchecked") FastSparseSet<Integer>[] arrnew = new FastSparseSet[length];
-        int[] arrnextnew = new int[length];
+        int[] arrnextnew = Arrays.copyOf(arrnext, length);
-
-        System.arraycopy(arrnext, 0, arrnextnew, 0, length);
 
         mapelements[i] = arrnew;
         mapnext[i] = arrnextnew;