/*-
 * ============LICENSE_START=======================================================
 * org.onap.dmaap
 * ================================================================================
 * Copyright (C) 2017 AT&T Intellectual Property. All rights reserved.
 * ================================================================================
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * ============LICENSE_END=========================================================
 */

package org.onap.dmaap.dbcapi.util;

import java.util.Random;

// source: http://stackoverflow.com/questions/41107/how-to-generate-a-random-alpha-numeric-string

public class RandomString {

	  private static final char[] symbols;

	  static {
	    StringBuilder tmp = new StringBuilder();
	    for (char ch = '0'; ch <= '9'; ++ch)
	      tmp.append(ch);
	    for (char ch = 'a'; ch <= 'z'; ++ch)
	      tmp.append(ch);
	    symbols = tmp.toString().toCharArray();
	  }   

	  private final Random random = new Random();

	  private final char[] buf;

	  public RandomString(int length) {
	    if (length < 1)
	      throw new IllegalArgumentException("length < 1: " + length);
	    buf = new char[length];
	  }

	  public String nextString() {
	    for (int idx = 0; idx < buf.length; ++idx) 
	      buf[idx] = symbols[random.nextInt(symbols.length)];
	    return new String(buf);
	  }
	}