是否有一个现有的Java实用程序方法可以联接“0”上的字符串列表&引用;及;“和”;?
我正在寻找一些东西来增强apache commons join()函数的功能,基本上这将实现makePrettyList()的功能是否有一个现有的Java实用程序方法可以联接“0”上的字符串列表&引用;及;“和”;?,java,string,utility-method,Java,String,Utility Method,我正在寻找一些东西来增强apache commons join()函数的功能,基本上这将实现makePrettyList()的功能 公共字符串makePrettyList(列表项){ String list=org.apache.commons.lang.StringUtils.join(items,“,”); int finalComma=list.lastIndexOf(“,”); 返回list.substring(0,finalComma)+”和“+list.substring(final
公共字符串makePrettyList(列表项){
String list=org.apache.commons.lang.StringUtils.join(items,“,”);
int finalComma=list.lastIndexOf(“,”);
返回list.substring(0,finalComma)+”和“+list.substring(finalComma+1,list.length());
}
makePrettyList([“Alpha”、“Beta”、“Omega”])-->“Alpha、Beta和Omega”如果您不打算使用第三方库,则需要编写自己的实用程序
public List<String> makePrettyList(List<String> items) {
StringBuilder builder = new StringBuilder();
for (int i = 0; i < items.size(); i++) {
if (i > 0) {
builder.append(" ");
if (i == items.size() - 1) {
builder.append("and ");
}
else {
builder.append(", ");
}
}
builder.append(items.get(i));
}
return builder.toString();
}
公共列表makePrettyList(列表项){
StringBuilder=新的StringBuilder();
对于(inti=0;i0){
生成器。追加(“”);
if(i==items.size()-1){
建造商。附加(“和”);
}
否则{
生成器。追加(“,”);
}
}
builder.append(items.get(i));
}
返回builder.toString();
}
[没有优雅地处理尾随和前导的空值/清空。现在效果更好。]
我的观点是,使用Google Guava(不是官方的Java,而是一套非常好的软件包)。我之所以提供它,是因为您似乎考虑过使用Joiner,但后来拒绝了它。既然您曾经开放使用Joiner,也许您想再看一次:
package testCode;
import java.util.List;
import com.google.common.base.Joiner;
import com.google.common.base.Predicate;
import com.google.common.base.Strings;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
public class TestClass {
Joiner joinComma = Joiner.on(", ");
Joiner joinAndForTwo = Joiner.on(" and ");
Joiner joinAndForMoreThanTwo = Joiner.on(", and ");
public String joinWithAnd(List<String> elements) {
ImmutableList<String> elementsNoNullsOrEmpties = new ImmutableList.Builder<String>()
.addAll(Iterables.filter(elements, new Predicate<String>() {
@Override
public boolean apply(String arg0) {
return !Strings.isNullOrEmpty(arg0);
}
})).build();
if (elementsNoNullsOrEmpties.size() == 0) {
return null;
} else if (elementsNoNullsOrEmpties.size() == 1) {
return Iterables.getOnlyElement(elementsNoNullsOrEmpties);
} else if (elementsNoNullsOrEmpties.size() == 2) {
return joinAndForTwo.join(elementsNoNullsOrEmpties);
} else {
final List<String> leadingElements = elementsNoNullsOrEmpties
.subList(0, elementsNoNullsOrEmpties.size() - 1);
final String trailingElement = elementsNoNullsOrEmpties
.get(elementsNoNullsOrEmpties.size() - 1);
return joinAndForMoreThanTwo.join(joinComma.join(leadingElements),
trailingElement);
}
}
}
包测试代码;
导入java.util.List;
导入com.google.common.base.Joiner;
导入com.google.common.base.Predicate;
导入com.google.common.base.Strings;
导入com.google.common.collect.ImmutableList;
导入com.google.common.collect.Iterables;
公共类TestClass{
Joiner Joine逗号=Joiner.on(“,”);
Joiner Joiner和Fortwo=Joiner.on(“和”);
Joiner Joiner and Formorethan=Joiner.on(“,and”);
公共字符串joinWithAnd(列表元素){
ImmutableList ElementsNonullsorPenttles=新建ImmutableList.Builder()
.addAll(Iterables.filter(元素,新谓词(){
@凌驾
公共布尔应用(字符串arg0){
return!Strings.isNullOrEmpty(arg0);
}
})).build();
if(elementsNonullsorEmptings.size()==0){
返回null;
}else if(elementsnonNullsor清空.size()==1){
返回Iterables.getOnlyElement(elementsNoNull或清空);
}else if(elementsnonNullsorEmptings.size()==2){
return join和fortwo.join(elementsnonNull或清空);
}否则{
最终列表leadingElements=ElementsNoNull或清空
.subList(0,elementsnowullsor清空.size()-1);
最终字符串trailingElement=ElementsNonullsorEmpts
.get(elementsnonNullsor清空.size()-1);
返回join和formorethan.join(joinComma.join(leadingElements),
拖带;
}
}
}
和测试驾驶员:
package testCode;
import java.util.List;
import com.google.common.collect.Lists;
public class TestMain {
static List<String> test1 = Lists.newArrayList();
static List<String> test2 = Lists.newArrayList("");
static List<String> test3 = Lists.newArrayList("a");
static List<String> test4 = Lists.newArrayList("a", "b");
static List<String> test5 = Lists.newArrayList("a", "b", "c", "d");
static List<String> test6 = Lists.newArrayList("a", "b", "c", null, "d");
static List<String> test7 = Lists.newArrayList("a", "b", "c", null);
static List<String> test8 = Lists.newArrayList("a", "b", "", "", null, "c",
null);
static List<String> test9 = Lists.newArrayList("", "a", "b", "c", null);
static List<String> test10 = Lists.newArrayList(null, "a", "b", "c", null);
public static void main(String[] args) {
TestClass testClass = new TestClass();
System.out.println(testClass.joinWithAnd(test1));
System.out.println(testClass.joinWithAnd(test2));
System.out.println(testClass.joinWithAnd(test3));
System.out.println(testClass.joinWithAnd(test4));
System.out.println(testClass.joinWithAnd(test5));
System.out.println(testClass.joinWithAnd(test6));
System.out.println(testClass.joinWithAnd(test7));
System.out.println(testClass.joinWithAnd(test8));
System.out.println(testClass.joinWithAnd(test9));
System.out.println(testClass.joinWithAnd(test10));
}
}
包测试代码;
导入java.util.List;
导入com.google.common.collect.list;
公共类TestMain{
静态列表test1=Lists.newArrayList();
静态列表test2=Lists.newArrayList(“”);
静态列表test3=Lists.newArrayList(“a”);
静态列表test4=Lists.newArrayList(“a”、“b”);
静态列表test5=Lists.newArrayList(“a”、“b”、“c”、“d”);
静态列表test6=Lists.newArrayList(“a”、“b”、“c”、null、“d”);
静态列表test7=Lists.newArrayList(“a”、“b”、“c”、null);
静态列表test8=Lists.newArrayList(“a”、“b”、“u”、“null”、“c”,
无效);
静态列表test9=Lists.newArrayList(“,”a“,”b“,”c“,”null);
静态列表test10=Lists.newArrayList(null,“a”,“b”,“c”,null);
公共静态void main(字符串[]args){
TestClass TestClass=新的TestClass();
System.out.println(testClass.joinWithAnd(test1));
System.out.println(testClass.joinWithAnd(test2));
System.out.println(testClass.joinWithAnd(test3));
System.out.println(testClass.joinWithAnd(test4));
System.out.println(testClass.joinWithAnd(test5));
System.out.println(testClass.joinWithAnd(test6));
System.out.println(testClass.joinWithAnd(test7));
System.out.println(testClass.joinWithAnd(test8));
System.out.println(testClass.joinWithAnd(test9));
System.out.println(testClass.joinWithAnd(test10));
}
}
以及输出:
空空
a
a和b
a、 b、c和d
a、 b、c和d
a、 b和c
a、 b和c
a、 b和c
a、 b和c
我喜欢这个,因为它不做任何字符串拼接。它对所提供的字符串列表进行分区,然后使用基于字符串元素数量的规则将它们正确地粘在一起,而无需返回并在事实之后反写“and”。我还处理出现在字符串列表开头、结尾或中间的空/空的各种边缘情况。可能是保证不会发生这种情况,因此可以简化此解决方案
[我的与你的有点不同,当我有两个元素时,我不会在第一个元素后和“and”之前加逗号,而对于三个或更多的元素,在“and”之前加逗号。这是一种风格。很容易调整到你喜欢的逗号应该如何工作。]这里有一个很好的方法,可以在需要的地方装饰/自定义
列表的实例
import java.util.*;
public class ListUtils
{
public static void main(final String[] args)
{
final List<String> sl = new ArrayList<String>()
{
public String toString()
{
final StringBuilder sb = new StringBuilder(this.size() * 512);
final ListIterator<String> li = this.listIterator();
while (li.hasNext())
{
if (li.nextIndex() == this.size() - 1)
{
sb.append("and ").append(li.next());
}
else if (li.nextIndex() == this.size() - 2)
{
sb.append(li.next()).append(" ");
}
else
{
sb.append(li.next()).append(", ");
}
}
return sb.toString();
}
};
// Test the output
sl.add("Alpha");
sl.add("Beta");
sl.add("Omega");
System.out.println(sl.toString());
}
}
您可以将这种构造的创建放在公共静态工厂方法中,并在需要时生成它们。如果您正在寻找Sun JDK的一部分,它并不存在,Apache Commons是获取此实用程序的常用方法之一(除了自己重新实现它之外)。这是相关的,@蝎子I哈
import java.util.*;
public class ListUtils
{
public static void main(final String[] args)
{
final List<String> sl = new ArrayList<String>()
{
public String toString()
{
final StringBuilder sb = new StringBuilder(this.size() * 512);
final ListIterator<String> li = this.listIterator();
while (li.hasNext())
{
if (li.nextIndex() == this.size() - 1)
{
sb.append("and ").append(li.next());
}
else if (li.nextIndex() == this.size() - 2)
{
sb.append(li.next()).append(" ");
}
else
{
sb.append(li.next()).append(", ");
}
}
return sb.toString();
}
};
// Test the output
sl.add("Alpha");
sl.add("Beta");
sl.add("Omega");
System.out.println(sl.toString());
}
}
Alpha, Beta and Omega