Java中动态地改变数组长度及数组转Map的代码实例分享_java

动态改变数组的长度

/** * Reallocates an array with a new size, and copies the contents
 * * of the old array to the new array.
 * * @param oldArray the old array, to be reallocated.
 * * @param newSize  the new array size.
 * * @return     A new array with the same contents.
 * */
private static Object resizeArray (Object oldArray, int newSize) {
  int oldSize = java.lang.reflect.Array.getLength(oldArray);
  Class elementType = oldArray.getClass().getComponentType();
  Object newArray = java.lang.reflect.Array.newInstance(
      elementType,newSize);
  int preserveLength = Math.min(oldSize,newSize);
  if (preserveLength > 0)
    System.arraycopy (oldArray,0,newArray,0,preserveLength);
  return newArray;  }
// Test routine for resizeArray().
public static void main (String[] args) {
  int[] a = {1,2,3};
  a = (int[])resizeArray(a,5);
  a[3] = 4;
  a[4] = 5;
  for (int i=0; i<a.length; i++)
    System.out.println (a[i]);
}

代码只是实现基础方法，详细处理还需要你去Coding哦>>

把 Array 转换成 Map

import java.util.Map;
import org.apache.commons.lang.ArrayUtils;
public class Main {
  public static void main(String[] args) {
    String[][] countries = { { "United States", "New York" },
        { "United Kingdom", "London" },
        { "Netherland", "Amsterdam" },
        { "Japan", "Tokyo" },
        { "France", "Paris" } };
    Map countryCapitals = ArrayUtils.toMap(countries);
    System.out.println("Capital of Japan is " + countryCapitals.get("Japan"));
    System.out.println("Capital of France is " + countryCapitals.get("France"));
}
} 

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