public static String getMaxSubString(String str1,String str2)
	{
		String max = null,min = null;
		if(str1.length()>str2.length())        //先區分出大串和小串
		{
			max = str1;
			min = str2;
		}
		else
		{
			max = str2;
			min = str1;
		}
		for(int x = 0;x<min.length();x++)        //外迴圈進行共同串的長度進行從大到小的遍歷
		{
			for(int a = 0,b = min.length()-x;b!=min.length()+1;a++,b++) //內部迴圈進行同一長度子串的查詢遍歷
			{
				String maxSub = min.substring(a, b);
				if(str1.contains(maxSub))
				{
					return maxSub;
				}
			}
		}
		return null;
	}
 

public static void main(String[] args) 
	{
		String str = "cr7goalx3wowcr7cr9ohcr7goalx1wowcr7goalx2cr7goalx2kingcr7goalx1biucr7goalx3woooowcr7goalx2"; 
		
		String sub = "cr7goalhicrcr9cr7goalx2wow";
		System.out.println(getMaxSubString(str,sub));
	}

結果：

cr7goalx2

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