substring 导致内存溢出

import java.util.ArrayList;
import java.util.List;

public class TestSubstring {
	
	public static void main(String[] args) {
		
		List<String> handler =new ArrayList<String>();
		int j = 0;
		
		for (int i = 0; i < 1000; i++) {
			j++;
			HugeStr h = new HugeStr();
			handler.add(h.getSubString(1,5));
		  System.out.println(j);
		}
	}
	
	static class HugeStr{
		
		private String str=new String(new char[100000]);
		
		public String getSubString(int begin,int end){
			
			return str.substring(begin, end);
		}
	}
	
	
	static class ImprovedHugeStr{
		
        private String str=new String(new char[100000]);
		
		public String getSubString(int begin,int end){
			
			return new String(str.substring(begin, end));
		}
	}
}import java.util.ArrayList;
import java.util.Li