关于动态数组 "Unexpected type" 的问题

Question

大家晚上好，打扰了
我在尝试自己配置“DynamicArray”时遇到问题。在这里我做了一个排序方法，但是终端显示“error:unexpected type”，我实际上很难解决这个问题，有人可以帮我检查一下我遇到了什么问题吗？
提前致谢。
这是我的代码：

package lab2;
public class DynamicArray {
  private static int INITIAL_CAPACITY = 5;
  private int[] data;
  private int size;
  public DynamicArray() {
    data = new int[INITIAL_CAPACITY];
    size = 0;
  }

  // Returns `true` if the array is empty.
  public boolean isEmpty() {
    if (size==0){
      return true;
    }
    else{
      return false;
    }
  }

  // Returns the size of the array.
  public int size() {
    return size;
  }

  // Remove all elements from data.
  public void clear() {
    size=0;
  }

  // Create a `String` with the elements of the array separated by comma, without a new line character at the end.
  // For instance: 4, 5, 6
  public String toString() {
    if(size==0){
      return "";
    }
    StringBuilder a = new StringBuilder();
    for(int i=0;i<size;i++){
      if(i==size-1){
        a.append(data[i]);
      }
      else{
        a.append(data[i]).append(",").append(" ");
      }
    }
    return a.toString();
  }

  // Returns `true` if the array `data` is full: no more element can be added to `data`.
  // Returns `false` otherwise.
  private boolean isFull() {
    if(size==data.length){
      return true;
    }
    return false;
  }

  // If the array `data` is full:
  //  1. Create a new array `data2` doubling the size of data.
  //  2. Copy the elements of `data` into `data2`.
  //  3. Assign `data2` to `data`.
  private void realloc() {
    if(size==data.length){
      int [] data2 = new int[data.length*2];
      System.arraycopy(data, 0, data2, 0,data.length);
      data=data2;
    }
  }

  // The element `x` is added to `data`, and `size` is incremented by one.
  // `data` is automatically resized if it is too small.
  public void add(int x) {
    realloc();
    data[size++]=x;
  }

  private void checkIndex(int idx) {
    if(idx >= size) {
      throw new ArrayIndexOutOfBoundsException();
    }
  }

  // Set the ith element of `data` to `x`.
  public void set(int idx, int x) {
    int a = data[idx];
    data[idx]=x;
  }

  // Return the element at the index `idx` of `data`.
  public int get(int idx) {
    checkIndex(idx);
    return data[idx];
  }

  // Remove the element at index `idx`.
  // Shift all the elements after `idx` of one position to the left.
  public void remove(int idx) {
    checkIndex(idx);
    for(int i = idx; i<size-1; i++){
      data[i]=data[i+1];
    }
    size--;
  }
}

以及出现问题的代码：

package lab2;

public class DynamicArrayTest {
  public static void main(String[] args) {
    DynamicArray array = new DynamicArray();
    testAdd(array);
    testRemove(array);
    testGet(array);
    testRealloc(array);
    testSort(array);
  }

  public static void testAdd(DynamicArray array) {
    System.out.println("Test add method.");
    System.out.println(array.size());
    System.out.println(array.isEmpty());
    array.clear();
    System.out.println(array.size());
    System.out.println(array.isEmpty());
    array.add(4);
    array.add(5);
    array.add(6);
    System.out.println(array);
  }

  public static void testRemove(DynamicArray array) {
    System.out.println("Test remove method.");
    try {
      for(int i = 0; i < 3; ++i) {
        array.remove(1);
        System.out.println(array);
        System.out.println(array.size());
        System.out.println(array.isEmpty());
      }
    }
    catch(ArrayIndexOutOfBoundsException e) {}
    array.remove(0);
    System.out.println(array);
    System.out.println(array.size());
    System.out.println(array.isEmpty());
  }

  public static void testGet(DynamicArray array) {
    System.out.println("Test get method.");
    try {
      array.get(4);
    }
    catch(ArrayIndexOutOfBoundsException e) {
      System.out.println("OK");
    }
  }

  public static void testRealloc(DynamicArray array) {
    System.out.println("Test realloc method.");
    for(int i = 0; i < 100; ++i) {
      array.add(i);
    }
    System.out.println(array);
    while(!array.isEmpty()) {
      array.remove(0);
    }
    System.out.println(array);
    System.out.println(array.size());
    System.out.println(array.isEmpty());
  }
  public static void testSort(DynamicArray array){
    System.out.println("Sort the array.");
    for(int i =0; i<array.size(); ++i){
      for (int j=0; j<array.size() - i; ++j){
        if (array.get(j-1)<array.get(j)){
          int a = array.get(j-1);
          array.get(j-1)=array.get(j);
          array.get(j)=a;
        }
      }
    }
  }
}

错误代码：


  public static void testSort(DynamicArray array){
    System.out.println("Sort the array.");
    for(int i =0; i<array.size(); ++i){
      for (int j=0; j<array.size() - i; ++j){
        if (array.get(j-1)<array.get(j)){
          int a = array.get(j-1);
          array.get(j-1)=array.get(j);
          array.get(j)=a;
        }
      }
    }
  }

再次，终端显示：

src/lab2/DynamicArrayTest.java:72: error: unexpected type
          array.get(j-1)=array.get(j);
                   ^
  required: variable
  found:    value
src/lab2/DynamicArrayTest.java:73: error: unexpected type
          array.get(j)=a;
                   ^
  required: variable
  found:    value
2 errors

非常感谢您的帮助。

Answer 1

array.get(j-1)=array.get(j);
array.get(j)=a;

应该是

array.set(j-1, array.get(j));
array.set(j, a);

Answer 2

此行试图为一个值赋值。该语句的左侧需要是一个变量。你在多个地方犯了同样的错误。

   array.get(j-1)=array.get(j);

您要么需要将 array.get(j) 的值赋给一个变量，要么在数组对象上调用 setter，将 j-1 的位置设置为 array.get(j)。取决于你想用这个值做什么。

关于动态数组 "Unexpected type" 的问题

Question about "Unexpected type" for Dynamic Array

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