[英]Java how to iterate through 3 arrayList
我创建了三个ArrayList
,并向它们添加了一些值。 然后,我遍历每个ArrayList
并希望根据if语句的条件更新值。 以下是我到目前为止已实现的代码,但未提供预期的输出:
List<String> columnNameList = new ArrayList<String>();
List<String> columnTypeList = new ArrayList<String>();
List<Integer> columnLengthList = new ArrayList<Integer>();
String result = "";
columnNameList.add("Id");
columnNameList.add("Name");
columnNameList.add("Address");
columnTypeList.add("char");
columnTypeList.add("varchar");
columnTypeList.add("varchar");
columnLengthList.add(18);
columnLengthList.add(50);
columnLengthList.add(10000);
outermostloop:
for (String name : columnNameList)
{
outerloop:
for (String type : columnTypeList)
{
loop:
for (int len : columnLengthList)
{
if(len > 0 && (!type.equalsIgnoreCase("int") && !type.equalsIgnoreCase("datetime") && !type.equalsIgnoreCase("datetime2")))
{
if(len > 8000 && !(name.equalsIgnoreCase("Id")) && (type.equalsIgnoreCase("varchar")))
{
result = name + " " + type + "(max) ";
System.out.println("if len > 8000 && name not id and type is varchar-> " + result);
// O/P expected : Address varchar(max)
}
else
{
String finalres = name + " " + type + "(" + len + ") ";
System.out.println("No conversion " + finalres);
/* O/P expected : Id char(18)
Name varchar(50)
*/
}
}
break outerloop;
}
}
}
List<String> columnNameList = new ArrayList<String>();
List<String> columnTypeList = new ArrayList<String>();
List<Integer> columnLengthList = new ArrayList<Integer>();
String result = "";
columnNameList.add("Id");
columnNameList.add("Name");
columnNameList.add("Address");
columnTypeList.add("char");
columnTypeList.add("varchar");
columnTypeList.add("varchar");
columnLengthList.add(18);
columnLengthList.add(50);
columnLengthList.add(10000);
/* outermostloop: for (String name : columnNameList) {
* outerloop: for (String type : columnTypeList) {
* loop: for (int len : columnLengthList) {
*/
for (int i = 0; i < columnNameList.size(); i++)
{
for (i = 0; i < columnTypeList.size(); i++)
{
for (i = 0; i < columnLengthList.size(); i++)
{
if(columnLengthList.get(i) > 0 && (!columnTypeList.get(i).equalsIgnoreCase("int") && !columnTypeList.get(i).equalsIgnoreCase("datetime") && !columnTypeList.get(i).equalsIgnoreCase("datetime2")))
{
if(columnLengthList.get(i) > 8000 && !(columnNameList.get(i).equalsIgnoreCase("Id")) && (columnTypeList.get(i).equalsIgnoreCase("varchar")))
{
result = columnNameList.get(i) + " " + columnTypeList.get(i) + "(max) ";
System.out.println("if len > 8000 && name not id and type is varchar " + result);
// O/P expected : Address varchar(max)
}
else
{
String finalres = columnNameList.get(i) + " " + columnTypeList.get(i) + "(" + columnLengthList.get(i) + ") ";
System.out.println("No conversion " + finalres);
/* O/P expected : Id char(18)
Name varchar(50)
*/
}
}
}
}
}
电流输出:
No conversion Id char(18) No conversion Name char(18) No conversion Address char(18)
预期产量:
No conversion Id char(18) No conversion Name varchar(50) if len > 8000 && name not id and type is varchar -> Address varchar(max)
我想我在break
时做错了什么。 谁能让我知道当前代码有什么问题,或者我缺少什么?
由于循环的结构,它不起作用。 outsidemostloop以“ Id”开头。 outsideloop以“ char”开头。 循环从18开始。现在,您的if子句得到评估。 之后,您将中断outerloop。 现在,outermostloop转到“名称”。 但是,outerloop再次使用“ char”从头开始。 循环也一样。
您可以将当前循环替换为
for(int i = 0; i < columnNameList.size(); i++){
然后替换:
name --> columnNameList.get(i)
type --> columnTypeList.get(i)
len --> columnLengthList.get(i)
另一个选择是将所有三个参数包装到您自己的类中,然后遍历该类的ArrayList。 例:
private class Column{
public String name;
public String type;
public int len;
public Column(String name, String type, int len){
this.name=name;
this.type=type;
this.len=len;
}
}
然后使用
ArrayList<Column> columns
和
columns.add(new Column("Id","Char",18));
等等...访问替换
name --> column.name
使用循环时
for(Column column: columns){
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