二维数组赋值报空指针

[tandy]

table = new String[td.size()][];	
		for (int i=0;i<td.size();i++) {
			table[k][j] = td.get(i);
			j++;
			if (j == 4) {
				k++;
				j = 0;
			}

td 是 List<String> td = new ArrayList<String>();
目的是将容器中的值 转化成二维数组，但是在从容器取值赋值给二维数组的时候报空指针错误 请问什么原因啊


Exception in thread "main" java.lang.NullPointerException
at bean.T_History.s_History(T_History.java:51)
at bean.T_History.main(T_History.java:21)

[tandy]

哪位大神帮看一下

[捡块砖头防身]

k，j怎么初始化的

[捡块砖头防身]

代码都没贴全

[于金龙]

这行代码

	List<String> td = new ArrayList<String>();

是你认为的吧。 看了你这段代码，包空指针就是td==null时，你对td求size报的 我给你的代码改为：

if(td==null){
 td = new ArrayList<String>();
}
table = new String[td.size()][];   
        for (int i=0;i<td.size();i++) {
            table[k][j] = td.get(i);
            j++;
            if (j == 4) {
                k++;
                j = 0;
            }

[tandy]

public String[][] s_History(String hy_number2) {	
		int k = 0;
		int j = 0;
		String[][]table;
		this.hy_number = hy_number2.trim();	
		Connection conn = DB.getConn();
		Statement stmt = DB.getStatement(conn);
		String sql = "select * from hy_history where hy_number="+"'"+hy_number+"' order by hy_sub_time desc";
		ResultSet rs = DB.getResultSet(stmt, sql);		
		try {
			while(rs.next()) {
				this.td.add ( rs.getString("hy_number"));
				this.td.add ( String.valueOf(rs.getInt("hy_sub_points")));
				this.td.add ( String.valueOf(rs.getInt("hy_points_now")));
				this.td.add ( rs.getString("operator"));
				this.td.add ( rs.getString("hy_sub_time"));
			}
			if(!rs.next()) {
				this.msg = "无此会员信息";
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
		
		table = new String[td.size()][];	
		for (int i=0;i<td.size();i++) {
			table[k][j] = td.get(i);
			j++;
			if (j == 4) {
				k++;
				j = 0;
			}
		}
		
		DB.closeRs(rs);
		DB.closeStmt(stmt);
		DB.closeConn(conn);	
		return table;
	
	}
	

[tandy]

多谢各位 找到原因了