如何重新排列数组以使空值占据数组的开头？

Question

我不确定如何将空元素添加到数组的前面。

有没有办法在不反转数组的情况下做到这一点？或许有具体的方法？

public static void main(String[] args) {

    String[] stringArray = new String[]{"one", "two", "three"};

    method(stringArray);

}

public static String[] method(String[] stringArray) {

    String[] biggerStringArray = Arrays.copyOf(stringArray, stringArray.length * 2);

    for (int i = 0; i < biggerStringArray.length; i++) {

        System.out.print(biggerStringArray[i] + ", ");

    }

    return biggerStringArray;

}

我希望结果看起来像：

空，空，空，一，二，三，

代替 ：

一、二、三、空、空、空

Answer 1

public static void main(String[] args) {&nbsp; &nbsp; String[] stringArray = new String[] {"one", "two", "three"};&nbsp; &nbsp; method(stringArray);&nbsp; }&nbsp; public static String[] method(String[] stringArray) {&nbsp; &nbsp; String[] biggerStringArray = new String[stringArray.length * 2];&nbsp; &nbsp; for (int i = 0; i < stringArray.length; i++) {&nbsp; &nbsp; &nbsp; biggerStringArray[i + biggerStringArray.length / 2] = stringArray[i];&nbsp; &nbsp; }&nbsp; &nbsp; for (int i = 0; i < biggerStringArray.length; i++) {&nbsp; &nbsp; &nbsp; System.out.print(biggerStringArray[i] + ", ");&nbsp; &nbsp; }&nbsp; &nbsp; return biggerStringArray;&nbsp; }编辑：刚刚记得您还可以使用System.arraycopy：public static String[] method(String[] stringArray) {&nbsp; &nbsp; String[] biggerStringArray = new String[stringArray.length * 2];&nbsp; &nbsp; System.arraycopy(stringArray, 0, biggerStringArray, biggerStringArray.length / 2, stringArray.length);&nbsp; &nbsp; for (int i = 0; i < biggerStringArray.length; i++) {&nbsp; &nbsp; &nbsp; System.out.print(biggerStringArray[i] + ", ");&nbsp; &nbsp; }&nbsp; &nbsp; return biggerStringArray;&nbsp; }

Answer 2

您可以首先创建一个长度等于stringArray. 然后，您可以stringArray使用任何 Java 数组连接方法将 与新的空数组连接起来。这是一个例子public static String[] method(String[] stringArray) {&nbsp; &nbsp; String[] nullArray = new String[stringArray.length];&nbsp; &nbsp; String[] biggerStringArray = Stream.of(nullArray, stringArray).flatMap(Stream::of).toArray(String[]::new);&nbsp; &nbsp; // for (int i = 0; i < biggerStringArray.length; i++) {&nbsp; &nbsp; //&nbsp; &nbsp; &nbsp;System.out.print(biggerStringArray[i] + ", ");&nbsp; &nbsp; // }&nbsp; &nbsp; return biggerStringArray;}

Answer 3

据我所知，不存在执行您正在寻找的操作的单个语句。但这并不意味着您不能自己做。有很多方法可以交换数组中的元素。这是一个：String[] biggerStringArray = Arrays.copyOf(stringArray, stringArray.length * 2);for(int i = 0; i < stringArray.length; i++){&nbsp; &nbsp; biggerStringArray[i] = biggerStringArray[i + stringArray.length];&nbsp; &nbsp; biggerStringArray[i + stringArray.length] = null;}

Answer 4

public static String[] method(String[]stringArray) {&nbsp; &nbsp; String[] biggerStringArray = Arrays.copyOf(stringArray, stringArray.length * 2);&nbsp; &nbsp; List<String> biggerStringList = Arrays.asList(biggerStringArray);&nbsp; &nbsp; biggerStringList.sort(Comparator.nullsFirst(String::compareTo));&nbsp; &nbsp; System.out.println(biggerStringList);&nbsp; &nbsp; return biggerStringList.toArray(new String[biggerStringList.size()]);}