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Java example source code file (GenericArray.java)

This example Java source code file (GenericArray.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

address, arrayindexoutofboundsexception, cinteger, cintfield, genericarray, object, observer, runtimeexception, type, util, vmobject, wrongtypeexception

The GenericArray.java Java example source code

package sun.jvm.hotspot.utilities;

import java.util.Observable;
import java.util.Observer;

import sun.jvm.hotspot.debugger.Address;
import sun.jvm.hotspot.oops.ArrayKlass;
import sun.jvm.hotspot.oops.CIntField;
import sun.jvm.hotspot.oops.Oop;
import sun.jvm.hotspot.runtime.VM;
import sun.jvm.hotspot.runtime.VMObject;
import sun.jvm.hotspot.types.AddressField;
import sun.jvm.hotspot.types.Type;
import sun.jvm.hotspot.types.TypeDataBase;
import sun.jvm.hotspot.types.WrongTypeException;

/**
 * The base class for the mirrors of the Array<T> C++ classes.
 */
public abstract class GenericArray extends VMObject {
  static {
    VM.registerVMInitializedObserver(new Observer() {
      public void update(Observable o, Object data) {
        initialize(VM.getVM().getTypeDataBase());
      }
    });
  }

  private static synchronized void initialize(TypeDataBase db) throws WrongTypeException {
    // Array<int> is arbitrarily chosen to get the fields in Array.
    Type type = db.lookupType("Array<int>");
    lengthField = new CIntField(type.getCIntegerField("_length"), 0);
  }

  private static long sizeOfArray;
  private static CIntField lengthField;

  private long dataFieldOffset;

  public GenericArray(Address addr, long dataOffset) {
    super(addr);
    dataFieldOffset = dataOffset;
  }

  public int length() {
    return (int)lengthField.getValue(this);
  }

  // for compatibility with TypeArray
  public int getLength() {
    return length();
  }

  /**
   * Gets the element at the given index.
   */
  protected long getIntegerAt(int index) {
    if (index < 0 || index >= length()) throw new ArrayIndexOutOfBoundsException(index + " " + length());

    Type elemType = getElemType();
    if (!getElemType().isCIntegerType()) throw new RuntimeException("elemType must be of CInteger type");

    Address data = getAddress().addOffsetTo(dataFieldOffset);
    long elemSize = elemType.getSize();

    return data.getCIntegerAt(index * elemSize, elemSize, false);
  }

  protected Address getAddressAt(int index) {
    if (index < 0 || index >= length()) throw new ArrayIndexOutOfBoundsException(index);

    Type elemType = getElemType();
    if (getElemType().isCIntegerType()) throw new RuntimeException("elemType must not be of CInteger type");

    Address data = getAddress().addOffsetTo(dataFieldOffset);
    long elemSize = elemType.getSize();

    return data.getAddressAt(index * elemSize);
  }

  private long byteSizeof(int length) { return sizeOfArray + length * getElemType().getSize(); }

  public long getSize() {
    return VM.getVM().alignUp(byteSizeof(length()), VM.getVM().getBytesPerWord()) / VM.getVM().getBytesPerWord();
  }

  /**
   * The element type of this array.
   */
  public abstract Type getElemType();
}

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