Random rnd=new Random; rnd.nextInt(20); 核心代码就在上面,至于你要生成20个数,那就创建一个长20的数组,用多个循环嵌套检查生成的数是不是和前面的元素有相同的,有就重新做,没有就赋值
1.random ra=new random (); ra.nextInt(20)+1; 2.Math.random()*20 用循环去掉重复
生产生顺序的序列,再随机进行交换import java.util.Random;public class Test {
public static void main(String args[]) { int[] n = getRandomSeries(20); for(int a : n) { System.out.print(a + " "); } }
public static int[] getRandomSeries(int size) { int[] series = new int[size]; for(int i = 0; i < size; i++) { series[i] = i + 1; } Random ran = new Random(); for(int i = 0, k = size * 2; i < k; i++) { int index1 = ran.nextInt(size); int tmp = series[index1]; int index2 = ran.nextInt(size); series[index1] = series[index2]; series[index2] = tmp; } return series; } }
List<Integer> list = new ArrayList<Integer>(); Random rnd = new Random(); for (int i = 0; i < 20; i++) { int j = rnd.nextInt(21); if (!list.contains(j) && j != 0) { list.add(j); } else { --i; } } Integer[] ii = list.toArray(new Integer[20]); Arrays.sort(ii); for (Integer i : ii) { System.out.println(i); }
BufferString s=""; for(int i=0;i<20;i++){ s.append(p()); } public static String p(){ int a=Math.radom()*200; String c=String.valueOf(a); int b=s.indexOf(c); if(b>=0) return c; else p(); }
import java.util.HashSet; import java.util.Set;public class Random { public static void main(String[] args) { boolean full=false; Set<Integer> s=new HashSet<Integer>(); int v; while(!full) {
StringBuffer buffer = new StringBuffer("ABCDEFGHIJKLMNOPQRSTUVWXYZ");
StringBuffer sb = new StringBuffer(); Random r = new Random(); int range = buffer.length(); for (int i = 0; i < 6; i ++) { sb.append(buffer.charAt(r.nextInt(range))); }
public static String getStringID(int length){ StringBuffer buffer = new StringBuffer("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ");
StringBuffer sb = new StringBuffer(); Random r = new Random(); int range = buffer.length(); for (int i = 0; i < length; i ++) { sb.append(buffer.charAt(r.nextInt(range))); } return sb.toString(); }
rnd.nextInt(20);
核心代码就在上面,至于你要生成20个数,那就创建一个长20的数组,用多个循环嵌套检查生成的数是不是和前面的元素有相同的,有就重新做,没有就赋值
ra.nextInt(20)+1;
2.Math.random()*20
用循环去掉重复
public static void main(String args[]) {
int[] n = getRandomSeries(20);
for(int a : n) {
System.out.print(a + " ");
}
}
public static int[] getRandomSeries(int size) {
int[] series = new int[size];
for(int i = 0; i < size; i++) {
series[i] = i + 1;
}
Random ran = new Random();
for(int i = 0, k = size * 2; i < k; i++) {
int index1 = ran.nextInt(size);
int tmp = series[index1];
int index2 = ran.nextInt(size);
series[index1] = series[index2];
series[index2] = tmp;
}
return series;
}
}
List<Integer> list = new ArrayList<Integer>();
Random rnd = new Random();
for (int i = 0; i < 20; i++) {
int j = rnd.nextInt(21);
if (!list.contains(j) && j != 0) {
list.add(j);
} else {
--i;
}
}
Integer[] ii = list.toArray(new Integer[20]);
Arrays.sort(ii);
for (Integer i : ii) {
System.out.println(i);
}
for(int i=0;i<20;i++){
s.append(p());
}
public static String p(){
int a=Math.radom()*200;
String c=String.valueOf(a);
int b=s.indexOf(c);
if(b>=0)
return c;
else
p();
}
import java.util.Set;public class Random { public static void main(String[] args) {
boolean full=false;
Set<Integer> s=new HashSet<Integer>();
int v;
while(!full) {
v=1+(int)(Math.random()*20);
s.add(v);
if(s.size()==20){
full=true;
}
}
System.out.println(s);
}}
import java.util.Set;public class Random { public static void main(String[] args) {
boolean full=false;
Set<Integer> s=new HashSet<Integer>();
int v;
while(!full) {
v=1+(int)(Math.random()*20);
s.add(v);
if(s.size()==20){
full=true;
}
}
System.out.println(s);
}}
StringBuffer buffer = new StringBuffer("ABCDEFGHIJKLMNOPQRSTUVWXYZ");
StringBuffer sb = new StringBuffer();
Random r = new Random();
int range = buffer.length();
for (int i = 0; i < 6; i ++)
{
sb.append(buffer.charAt(r.nextInt(range)));
}
SimpleDateFormat formate2=new SimpleDateFormat("yyMMddmmssSSS");
String bb = formate2.format(new Date());
String temp1 = sb.toString();
String temp2 = temp1.substring(0,4);
String id = "F"+temp1.substring(0,3)+bb.substring(0,2)+temp1.substring(4,6)+bb.substring(bb.length()-2,bb.length());
System.out.println("F"+temp1.substring(0,3)+bb.substring(0,2)+temp1.substring(4,6)+bb.substring(bb.length()-2,bb.length())); return id;
}
public static String getStringID(int length){
StringBuffer buffer = new StringBuffer("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ");
StringBuffer sb = new StringBuffer();
Random r = new Random();
int range = buffer.length();
for (int i = 0; i < length; i ++)
{
sb.append(buffer.charAt(r.nextInt(range)));
} return sb.toString();
}