随机产生50[20-40]个数字，求出每个数子出现的次数

import java.util.Random;

public class TestExce {
public String generateStr2() {

String result = "";
int[] arr = new int[50];
Random random = new Random();
// 1. 随机产生50[20-40]个数字，求出每个数子出现的次数
for (int i = 0; i < 50; i++) {
int value = random.nextInt(21) + 20;
arr[value] += 1;
}
StringBuilder builder =new StringBuilder();
for (int i = 20; i <=40; i++) {
if (arr[i]!=0){
builder.append(i).append("(").append(arr[i]).append(")");
//System.out.println(i+"=次数=" + index);

}
}
return builder.toString();
}

public String generateStr() {

String result = "";
int[] arr = new int[41];
Random random = new Random();
// 1. 随机产生50[20-40]个数字，求出每个数子出现的次数
for (int i = 0; i < 50; i++) {
int value = random.nextInt(21) + 20; 
arr[value]=arr[value]+1;
//arr[i] = value;
}
StringBuilder builder =new StringBuilder();
for (int j = 20; j <41; j++) {
int index =arr[j];
if(index>0){
builder.append(j).append("(").append(index).append(") "); 
}
}
return builder.toString();
}

/**
* @param args
*/
public static void main(String[] args) {

TestExce testExce = new TestExce();
String str = testExce.generateStr();
System.out.println(str);

}

}