请高手来看看数组下标溢出解决思路

请高手来看看数组下标溢出
//找出两个字符串中所有相同的子串
import java.util.*;
public class 找出共同的子串 {
public static void FindSon(String str1,String str2)
{
String a[]=new String[(str1.length()+1)*str1.length()/2];
String b[]=new String[(str2.length()+1)*str2.length()/2]; //获得str1和str2的子串总数
int x=0,y=0;
for(int i=0;i<str1.length();i++)
{
for(int j=i+1;j<=str1.length();j++)
{
a[x]=str1.substring(i,j);
x++;
}
}

for(int i=0;i<str2.length();i++)
{
for(int j=i+1;j<=str2.length();j++)
{

b[y]=str2.substring(i,j);
y++;
}
}
for(int i=0;i<a.length;i++)
{
int k=0;
for(int j=0;j<b.length;j++)
{
if(a[i].equals(b[i]))
{
k++;
}
}
if(k>0)System.out.print(a[i]+" ");

}

}
public static void main(String args[]) {
// TODO Auto-generated method stub
System.out.println("输入两个字符串：");
Scanner sc=new Scanner(System.in);
String str1=sc.next();
String str2=sc.next();
FindSon(str1,str2);
}

}



a[x]=str1.substring(i,j);
为什么这里赋不了值？
没报错，运行后没反映

[解决办法]

Java code

    for (int i = 0; i < a.length; i++) {            int k = 0;            for (int j = 0; j < b.length; j++) {                if (a[i].equals(b[i])) {                    k++;                }            }            if (k > 0)                System.out.print(a[i] + " ");        }
[解决办法]
你这段代码计算结果不明朗，给你优化一下
Java code
public class FindSon3 {    public static void FindSon(String str1, String str2) {        HashMap setStr1 = new HashMap();        HashMap setStr2 = new HashMap();        int x = 0, y = 0, p = 0, q = 0;                for (int i = 0; i < str1.length(); i++) {            for (int j = i + 1; j <= str1.length(); j++) {                if (!setStr1.containsValue(str1.substring(i, j))) {                    setStr1.put(p, str1.substring(i, j));                    x++;                    p++;                }            }        }        for (int i = 0; i < str2.length(); i++) {            for (int j = i + 1; j <= str2.length(); j++) {                if (!setStr2.containsValue(str2.substring(i, j))) {                    setStr2.put(q, str2.substring(i, j));                    y++;                    q++;                }            }        }        System.out.println();        for (int i = 0; i < setStr1.size(); i++) {            int k = 0;            for (int j = 0; j < setStr2.size(); j++) {                if (setStr1.get(i).equals(setStr2.get(j))) {                    k++;                }            }            if (k > 0)                System.out.print(setStr1.get(i) + " ");        }    }    public static void main(String args[]) {        // TODO Auto-generated method stub        System.out.println("输入两个字符串：");        Scanner sc = new Scanner(System.in);        String str1 = sc.next();        String str2 = sc.next();        FindSon(str1, str2);    }}