Android 使用Random生成随机数

/**
* 随机数、字母 工具类
* Created by admin on 2017/2/20.
*/
public class RandomUntil {

/**
* 生成一个0 到 count 之间的随机数
* @param endNum
* @return
*/
public static int getNum(int endNum){
if(endNum > 0){
Random random = new Random();
return random.nextInt(endNum);
}
return 0;
}

/**
* 生成一个startNum 到 endNum之间的随机数(不包含endNum的随机数)
* @param startNum
* @param endNum
* @return
*/
public static int getNum(int startNum,int endNum){
if(endNum > startNum){
Random random = new Random();
return random.nextInt(endNum - startNum) + startNum;
}
return 0;
}

/**
* 生成随机大写字母
* @return
*/
public static String getLargeLetter(){
Random random = new Random();
return String.valueOf ((char) (random.nextInt(27) + 'A'));
}

/**
* 生成随机大写字母字符串
* @return
*/
public static String getLargeLetter(int size){
StringBuffer buffer = new StringBuffer();
Random random = new Random();
for(int i=0; i<size;i++){
buffer.append((char) (random.nextInt(27) + 'A'));
}
return buffer.toString();
}

/**
* 生成随机小写字母
* @return
*/
public static String getSmallLetter(){
Random random = new Random();
return String.valueOf ((char) (random.nextInt(27) + 'a'));
}

/**
* 生成随机小写字母字符串
* @return
*/
public static String getSmallLetter(int size){
StringBuffer buffer = new StringBuffer();
Random random = new Random();
for(int i=0; i<size;i++){
buffer.append((char) (random.nextInt(27) + 'a'));
}
return buffer.toString();
}

/**
* 数字与小写字母混编字符串
* @param size
* @return
*/
public static String getNumSmallLetter(int size){
StringBuffer buffer = new StringBuffer();
Random random = new Random();
for(int i=0; i<size;i++){
if(random.nextInt(2) % 2 == 0){//字母

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buffer.append((char) (random.nextInt(27) + 'a'));
}else{//数字
buffer.append(random.nextInt(10));
}
}
return buffer.toString();
}

/**
* 数字与大写字母混编字符串
* @param size
* @return
*/
public static String getNumLargeLetter(int size){
StringBuffer buffer = new StringBuffer();
Random random = new Random();
for(int i=0; i<size;i++){
if(random.nextInt(2) % 2 == 0){//字母
buffer.append((char) (random.nextInt(27) + 'A'));
}else{//数字
buffer.append(random.nextInt(10));
}
}
return buffer.toString();
}

/**
* 数字与大小写字母混编字符串
* @param size
* @return
*/
public static String getNumLargeSmallLetter(int size){
StringBuffer buffer = new StringBuffer();
Random random = new Random();
for(int i=0; i<size;i++){
if(random.nextInt(2) % 2 == 0){//字母
if(random.nextInt(2) % 2 == 0){
buffer.append((char) (random.nextInt(27) + 'A'));
}else{
buffer.append((char) (random.nextInt(27) + 'a'));
}
}else{//数字
buffer.append(random.nextInt(10));
}
}
return buffer.toString();
}

}