最好的Java5种遍历HashMap数据的写法

通过EntrySet的迭代器遍历

Iterator < Entry < Integer, String >> iterator = coursesMap.entrySet().iterator();
while (iterator.hasNext()) {
    Entry < Integer, String > entry = iterator.next();
    System.out.print(entry.getKey() + ". ");
    System.out.println(entry.getValue());
}

输出结果如下：

zzw:how_iterate_hashmap_in_java zzw$ java IterateHashMapExample 1
TIOBE Index for March 2020:
1. Java
2. C
3. Python
4. C++
5. C#
6. Visual Basic .NET
7. JavaScript
8. PHP
9. SQL
10. GO

通过KeySet的迭代器遍历

Iterator < Integer > iterator = coursesMap.keySet().iterator();
while (iterator.hasNext()) {
    Integer key = iterator.next();
    System.out.print(key + ". ");
    System.out.println(coursesMap.get(key));
}

输出结果如下：

zzw:how_iterate_hashmap_in_java zzw$ java IterateHashMapExample 2
TIOBE Index for March 2020:
1. Java
2. C
3. Python
4. C++
5. C#
6. Visual Basic .NET
7. JavaScript
8. PHP
9. SQL
10. GO

通过ForEach循环遍历

for (Map.Entry < Integer, String > entry: coursesMap.entrySet()) {
    System.out.print(entry.getKey() + ". ");
    System.out.println(entry.getValue());
}

输出结果如下：

zzw:how_iterate_hashmap_in_java zzw$ java IterateHashMapExample 3
TIOBE Index for March 2020:
1. Java
2. C
3. Python
4. C++
5. C#
6. Visual Basic .NET
7. JavaScript
8. PHP
9. SQL
10. GO

通过Lambda表达式遍历

coursesMap.forEach((key, value) -> {
    System.out.print(key + ". ");
    System.out.println(value);
});

输出结果如下：

zzw:how_iterate_hashmap_in_java zzw$ java IterateHashMapExample 4
TIOBE Index for March 2020:
1. Java
2. C
3. Python
4. C++
5. C#
6. Visual Basic .NET
7. JavaScript
8. PHP
9. SQL
10. GO

通过Stream API遍历

coursesMap.entrySet().stream().forEach((entry) -> {
    System.out.print(entry.getKey() + ". ");
    System.out.println(entry.getValue());
});

输出结果如下：

zzw:how_iterate_hashmap_in_java zzw$ java IterateHashMapExample 5
TIOBE Index for March 2020:
1. Java
2. C
3. Python
4. C++
5. C#
6. Visual Basic .NET
7. JavaScript
8. PHP
9. SQL
10. GO

部分代码截图如下：

how_iterate_hashmap_in_java.png

完整示例代码在这里