MemoryUtil.java

package hamaster.gradesgin.util;

import java.math.BigInteger;
import java.security.SecureRandom;
import java.util.Random;

/**
 * 安全清理内存的工具类
 * @author <a href="mailto:wangyeee@gmail.com">Wang Ye</a>
 */
final public class MemoryUtil {

	/**
	 * 在新的线程中安全擦除内存块，这个方法在执行后会快速返回<br>
	 * 此方法与在新线程中执行immediateSecureBuffers方法等效
	 * @param buffers 待擦除的内存块
	 */
	public final static void fastSecureBuffers(byte[] ... buffers) {
		new SecureBufferThread(buffers).start();
	}

	/**
	 * 立刻安全擦除内存块
	 * @param buffers 待擦除的内存块
	 */
	public final static void immediateSecureBuffers(byte[] ... buffers) {
		BigInteger i = new BigInteger(Long.toHexString(System.nanoTime()), 16);
		Random random = new SecureRandom(i.toByteArray());
		for (byte[] buffer : buffers) {
			if (buffer != null)
				random.nextBytes(buffer);
		}
	}
}

final class SecureBufferThread extends Thread {

	private byte[][] buffers;

	public SecureBufferThread(byte[] ... buffers) {
		this.buffers = buffers;
	}

	@Override
	public void run() {
		MemoryUtil.immediateSecureBuffers(this.buffers);
	}
}