Java 打印树形图<;字符串,树集<;字符串>&燃气轮机;键和映射值
我试过了Java 打印树形图<;字符串,树集<;字符串>&燃气轮机;键和映射值,java,printing,Java,Printing,我试过了 Heat Bosh Lebron Wade Nets DWill KG Sonics Warriors Curry Iggy Thompson 但这也不完全正确,它的输出是 for ( String w : listNBA){ System.out.print( w + " "); if (treemap.containsKey(w)) System.out.println
Heat Bosh Lebron Wade
Nets DWill KG
Sonics
Warriors Curry Iggy Thompson
但这也不完全正确,它的输出是
for ( String w : listNBA){
System.out.print( w + " ");
if (treemap.containsKey(w))
System.out.println(treemap.get(w));
else
System.out.println( "" ); // print nothing if team doesn't exist
所以,我的问题是:在我的print方法中,有没有简单的方法将TreeSet转换为字符串?您可以遍历条目集并打印出键和相应的值
Heat [Bosh, Lebron, Wade]
Nets [DWill, KG]
Sonics null
Warriors [Curry,Iggy,Thompson]
for(Map.Entry:treemap.entrySet())
{
System.out.print(entry.getKey()+);
System.out.print(entry.getValue());
}
您可以执行以下操作:
for(Map.Entry<String, TreeSet <String>> entry : treemap.entrySet())
{
System.out.print( entry.getKey() + " ");
System.out.print( entry.getValue());
}
StringBuilder StringBuilder=新建StringBuilder();
for(条目映射条目:treemap.entrySet()){
append(mapEntry.getKey());
if(mapEntry.getValue()!=null){
for(字符串setEntry:mapEntry.getValue()){
stringBuilder.append(“”).append(setEntry);
}
}
stringBuilder.append(“\n”);
}
System.out.println(stringBuilder.toString());
Java 8有一个字符串。join
方法非常适合:
StringBuilder stringBuilder = new StringBuilder();
for (Entry<String, TreeSet<String>> mapEntry : treemap.entrySet()) {
stringBuilder.append(mapEntry.getKey());
if (mapEntry.getValue() != null) {
for (String setEntry : mapEntry.getValue()) {
stringBuilder.append(" ").append(setEntry);
}
}
stringBuilder.append("\n");
}
System.out.println(stringBuilder.toString());
请注意,当原始的System.out.println(treemap.get(w))
打印出null
时,如果get
方法返回null
,String.join
将在获取null参数时抛出NullPointerException
。因此,我在前面的if
中添加了一个空检查
join
的第一个参数是将插入每个输入字符串之间的字符串。它可以接受数量可变的String
(或任何其他CharSequence
)参数,也可以接受String
(或其他CharSequence
)数组。对于每个键,对于对应值中的每个元素。。。
StringBuilder stringBuilder = new StringBuilder();
for (Entry<String, TreeSet<String>> mapEntry : treemap.entrySet()) {
stringBuilder.append(mapEntry.getKey());
if (mapEntry.getValue() != null) {
for (String setEntry : mapEntry.getValue()) {
stringBuilder.append(" ").append(setEntry);
}
}
stringBuilder.append("\n");
}
System.out.println(stringBuilder.toString());
for ( String w : listNBA){
System.out.print( w + " ");
if (treemap.containsKey(w) && treemap.get(w) != null)
System.out.println(String.join(" ",treemap.get(w)));
else
System.out.println( "" ); // print nothing if team doesn't exist
}