无法导入Map.Entry

Question

我在导入Map.Entry时遇到问题。即使我有import import java.util.Map.Entry -也有一个错误："The import java.util.Map.Entry cannot be resolved“。并且entrySet()方法不起作用。有什么问题吗？(我使用jre8)

import java.io.File;
import java.util.LinkedHashMap;
import java.util.Map;

import java.util.Set;

import org.biojava3.core.sequence.ProteinSequence;
import org.biojava3.core.sequence.io.FastaReaderHelper;




public class Main {

/**
 * @param args
 */
public static void main(String[] args) throws Exception {
    LinkedHashMap<String, ProteinSequence> a = FastaReaderHelper.readFastaProteinSequence(new File("A2RTH4.fasta"));

    for (Map.Entry<String, ProteinSequence> entry : a.entrySet(); //entrySet A map entry (key-value pair). 
    {
        System.out.println( entry.getValue().getOriginalHeader() + "=" + entry.getValue().getSequenceAsString() );
    }
    }

}

Answer 1

for(Map.Entry<String, Integer> entry : someMap.entrySet())

仅适用于import java.util.Map导入。

Answer 2

import java.util.Map就足够了

尝试这段代码，应该是有效的：

public static void main(String[] args) throws Exception {
LinkedHashMap<String, ProteinSequence> a = FastaReaderHelper.readFastaProteinSequence(new File("A2RTH4.fasta"));
Set entrySet = a.entrySet();
Iterator it = entrySet.iterator();
// Iterate through LinkedHashMap entries
System.out.println("LinkedHashMap entries : ");
while(it.hasNext())
  System.out.println(it.next());
  }
}

尝试使用迭代器遍历LinkedHashMap数据结构，而不是foreach。

Answer 3

for (Map.Entry<String, ProteinSequence> entry : a.entrySet();

应该是

for (Map.Entry<String, ProteinSequence> entry : a.entrySet())

(结束括号而不是分号)。