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Accent4J is a suite of libraries, helpers and data structures that make Java programming idioms more fluent.
/*
* Copyright (c) 2016 Cinchapi Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.cinchapi.common.base;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.List;
import com.cinchapi.common.reflect.Reflection;
/**
* A builder for arrays.
*
* Use an {@link ArrayBuilder} when there is a need to efficiently produce
* arrays with an unknown length.
*
*
* When trying to construct an array of an unknown length, you can create a
* {@link List} and use the {@link List#toArray()} method, but this approach is
* ugly and inefficient. This builder provides a much more fluent syntax and
* minimizes the amount of memory necessary to build the array dynamically.
*
*
* @author Jeff Nelson
*/
public class ArrayBuilder {
/**
* Return a new {@link ArrayBuilder}.
*
* @return the builder
*/
public static ArrayBuilder builder() {
return new ArrayBuilder();
}
/**
* The number of elements that have been {@link #add(Object) added} to
* the array.
*/
private int length = 0;
/**
* The first 10 args are assigned to instance variables for memory
* efficiency.
*/
private T arg0 = null;
/**
* The first 10 args are assigned to instance variables for memory
* efficiency.
*/
private T arg1 = null;
/**
* The first 10 args are assigned to instance variables for memory
* efficiency.
*/
private T arg2 = null;
/**
* The first 10 args are assigned to instance variables for memory
* efficiency.
*/
private T arg3 = null;
/**
* The first 10 args are assigned to instance variables for memory
* efficiency.
*/
private T arg4 = null;
/**
* The first 10 args are assigned to instance variables for memory
* efficiency.
*/
private T arg5 = null;
/**
* The first 10 args are assigned to instance variables for memory
* efficiency.
*/
private T arg6 = null;
/**
* The first 10 args are assigned to instance variables for memory
* efficiency.
*/
private T arg7 = null;
/**
* The first 10 args are assigned to instance variables for memory
* efficiency.
*/
private T arg8 = null;
/**
* The first 10 args are assigned to instance variables for memory
* efficiency.
*/
private T arg9 = null;
/**
* A {@link List} that holds any remaining args after the first 10 have been
* added.
*/
private List moreArgs = null;
private Class type;
/**
* Construct a new instance.
*/
private ArrayBuilder() {/* no-op */}
/**
* Add all the {@code args} to the array.
*
* @param args the arg to add
* @return this
*/
public ArrayBuilder add(T[] args) {
for (T arg : args) {
add(arg);
}
return this;
}
/**
* Add {@code arg} to the array.
*
* @param arg the arg to add
* @return this
*/
public ArrayBuilder add(T arg) {
switch (length) {
case 0:
arg0 = arg;
break;
case 1:
arg1 = arg;
break;
case 2:
arg2 = arg;
break;
case 3:
arg3 = arg;
break;
case 4:
arg4 = arg;
break;
case 5:
arg5 = arg;
break;
case 6:
arg6 = arg;
break;
case 7:
arg7 = arg;
break;
case 8:
arg8 = arg;
break;
case 9:
arg9 = arg;
break;
default:
if(moreArgs == null) {
moreArgs = new ArrayList();
}
moreArgs.add(arg);
break;
}
++length;
type = (type == null || arg.getClass() == type) ? arg.getClass()
: Reflection.getClosestCommonAncestor(type, arg.getClass());
return this;
}
/**
* Build the array.
*
* @return the array
*/
@SuppressWarnings("unchecked")
public T[] build() {
if(arg0 == null) {
throw new IllegalStateException();
}
else {
T[] array = (T[]) Array.newInstance(type, length);
T current = arg0;
boolean exit = false;
int index = 0;
while (!exit) {
if(current == null) {
exit = true;
continue;
}
else {
array[index] = current;
switch (index) {
case 0:
current = arg1;
break;
case 1:
current = arg2;
break;
case 2:
current = arg3;
break;
case 3:
current = arg4;
break;
case 4:
current = arg5;
break;
case 5:
current = arg6;
break;
case 6:
current = arg7;
break;
case 7:
current = arg8;
break;
case 8:
current = arg9;
break;
default:
current = null;
break;
}
++index;
continue;
}
}
if(length > 10) {
for (T arg : moreArgs) {
array[index] = arg;
++index;
}
}
return array;
}
}
/**
* Return the the number of items that have been added.
*
* @return the length of the array that will be {@link #build() built}
*/
public int length() {
return length;
}
}
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