Map遍历的时间比较
map的四种遍历方法，点此查看
具体测试代码如下：
int num = 1000000;
final Map<Integer, String> map = new HashMap<Integer, String>(num);
System.out.println("map设值");
for (int i = 0; i < num; i++) {
map.put(i, UUID.randomUUID().toString());
}
System.out.println("entrySet方法：可以同时获取key和value，推荐这种方法");
FbJobResult result = Freebencher.benchmark(new FbTarget() { //the behavior
@Override
public boolean invoke() {
Set<Map.Entry<Integer, String>> entrySet = map.entrySet();
for (Map.Entry<Integer, String> entry : entrySet) {
Integer key = entry.getKey();
String value = entry.getValue();
}
return true;
}
}, 10, // concurrency,
10 // number of tests to run
);
System.out.println("-------entrySet方法时间----------");
System.out.println(result.report());
System.out.println("*****************************************");
System.out.println("keySet方法：先获取key，再获取value");
final Set<Integer> keySet = map.keySet();
result = Freebencher.benchmark(new FbTarget() { //the behavior
@Override
public boolean invoke() {
for (Integer key : keySet) {
String value = map.get(key);
}
return true;
}
}, 10, // concurrency,
10 // number of tests to run
);
System.out.println("-------keySet方法时间----------");
System.out.println(result.report());
System.out.println("*****************************************");
System.out.println("values方法：只获取value");
result = Freebencher.benchmark(new FbTarget() { //the behavior
@Override
public boolean invoke() {
Collection<String> values = map.values();
for (String value : values) {
}
return true;
}
}, 10, // concurrency,
10 // number of tests to run
);
System.out.println("-------values方法时间----------");
System.out.println(result.report());
System.out.println("*****************************************");
System.out.println("entrySet.iterator方法：迭代器");
result = Freebencher.benchmark(new FbTarget() { //the behavior
@Override
public boolean invoke() {
Iterator<Map.Entry<Integer, String>> iterator = map.entrySet().iterator();
while (iterator.hasNext()) {
Map.Entry<Integer, String> next = iterator.next();
Integer key = next.getKey();
String value = next.getValue();
}
return true;
}
}, 10, // concurrency,
10 // number of tests to run
);
System.out.println("-------entrySet.iterator方法时间----------");
System.out.println(result.report());
System.out.println("*****************************************");
下面查看四种遍历消耗1000000条数据的消耗时间，测试方法用到的工具包是Freebencher
map设值 entrySet方法：可以同时获取key和value，推荐这种方法 Test started. Awaiting termination... Test completed. -------entrySet方法时间---------- Concurrency: 10 Time taken for tests: 112ms Successful tests: 10 Failed tests: 0 Tests per second: 89.28571428571429 Mean time per test: 88.2ms Percentage of the test finished within a certain time (ms) 50%: 88 60%: 93 70%: 101 80%: 104 90%: 109 95%: 110 98%: 110 99%: 110 100%: 110 ***************************************** keySet方法：先获取key，再获取value Test started. Awaiting termination... Test completed. -------keySet方法时间---------- Concurrency: 10 Time taken for tests: 218ms Successful tests: 10 Failed tests: 0 Tests per second: 45.87155963302752 Mean time per test: 182.5ms Percentage of the test finished within a certain time (ms) 50%: 183 60%: 211 70%: 214 80%: 215 90%: 215 95%: 216 98%: 216 99%: 216 100%: 216 ***************************************** values方法：只获取value Test started. Awaiting termination... Test completed. -------values方法时间---------- Concurrency: 10 Time taken for tests: 123ms Successful tests: 10 Failed tests: 0 Tests per second: 81.30081300813008 Mean time per test: 96.2ms Percentage of the test finished within a certain time (ms) 50%: 105 60%: 107 70%: 109 80%: 111 90%: 113 95%: 115 98%: 115 99%: 115 100%: 115 ***************************************** entrySet.iterator方法：迭代器 Test started. Awaiting termination... Test completed. -------entrySet.iterator方法时间---------- Concurrency: 10 Time taken for tests: 103ms Successful tests: 10 Failed tests: 0 Tests per second: 97.0873786407767 Mean time per test: 82.6ms Percentage of the test finished within a certain time (ms) 50%: 83 60%: 90 70%: 91 80%: 94 90%: 97 95%: 103 98%: 103 99%: 103 100%: 103 *****************************************
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