Groovy学习-map操作

拼搏现实的明天。 2022-10-25 05:52 254阅读 0赞

### 创建和获取 ###

def map = [name: 'Gromit', likes: 'cheese', id: 1234]
    assert map.get('name') == 'Gromit'
    assert map.get('id') == 1234
    assert map['name'] == 'Gromit'
    assert map['id'] == 1234
    assert map instanceof java.util.Map
    
    def emptyMap = [:]
    assert emptyMap.size() == 0
    emptyMap.put("foo", 5)
    assert emptyMap.size() == 1
    assert emptyMap.get("foo") == 5

### map字面值 ###

def a = 'Bob'
    def ages = [a: 43]
    assert ages['Bob'] == null // 找不到`Bob`
    assert ages['a'] == 43     // 因为 `a` 是字面值（文本）!
    
    ages = [(a): 43]            // 将`a`用()括起来
    assert ages['Bob'] == 43   // 这时就能找到'Bob'的值了

### 拷贝副本 ###

def map = [
            simple : 123,
            complex: [a: 1, b: 2]
    ]
    def map2 = map.clone()
    assert map2.get('simple') == map.get('simple')
    assert map2.get('complex') == map.get('complex')
    map2.get('complex').put('c', 3)
    assert map.get('complex').get('c') == 3

### map属性符号 ###

def map = [name: 'Gromit', likes: 'cheese', id: 1234]
    assert map.name == 'Gromit'     // 同map.get('Gromit')
    assert map.id == 1234
    
    def emptyMap = [:]
    assert emptyMap.size() == 0
    emptyMap.foo = 5
    assert emptyMap.size() == 1
    assert emptyMap.foo == 5

### 部分标识符操作 ###

def map = [name: 'Gromit', likes: 'cheese', id: 1234]
    assert map.class == null
    assert map.get('class') == null
    assert map.getClass() == LinkedHashMap // 这很可能是你想要的结果
    
    map = [1      : 'a',
           (true) : 'p',
           (false): 'q',
           (null) : 'x',
           'null' : 'z']
    assert map.containsKey(1) // 数字1不是一个标识符，所以得这样调用
    assert map.true == null
    assert map.false == null
    assert map.get(true) == 'p'
    assert map.get(false) == 'q'
    assert map.null == 'z'
    assert map.get(null) == 'x'

### map迭代 ###

def map = [
            Bob  : 42,
            Alice: 54,
            Max  : 33
    ]
    
    // `entry` is a map entry
    map.each { entry ->
        println "Name: $entry.key Age: $entry.value"
    }
    
    // `entry` is a map entry, `i` the index in the map
    map.eachWithIndex { entry, i ->
        println "$i - Name: $entry.key Age: $entry.value"
    }
    
    // Alternatively you can use key and value directly
    map.each { key, value ->
        println "Name: $key Age: $value"
    }
    
    // Key, value and i as the index in the map
    map.eachWithIndex { key, value, i ->
        println "$i - Name: $key Age: $value"
    }

### 添加或删除元素 ###

def defaults = [1: 'a', 2: 'b', 3: 'c', 4: 'd']
    def overrides = [2: 'z', 5: 'x', 13: 'x']
    
    def result = new LinkedHashMap(defaults)
    result.put(15, 't')
    result[17] = 'u'
    result.putAll(overrides)
    assert result == [1: 'a', 2: 'z', 3: 'c', 4: 'd', 5: 'x', 13: 'x', 15: 't', 17: 'u']
    
    def m = [1:'a', 2:'b']
    assert m.get(1) == 'a'
    m.clear() // 删除所有元素
    assert m == [:]

### 分组 ###

assert ['a', 7, 'b', [2, 3]].groupBy {
        it.class
    } == [(String)   : ['a', 'b'],
          (Integer)  : [7],
          (ArrayList): [[2, 3]]
    ]
    
    assert [
            [name: 'Clark', city: 'London'], [name: 'Sharma', city: 'London'],
            [name: 'Maradona', city: 'LA'], [name: 'Zhang', city: 'HK'],
            [name: 'Ali', city: 'HK'], [name: 'Liu', city: 'HK'],
    ].groupBy { it.city } == [
            London: [[name: 'Clark', city: 'London'],
                     [name: 'Sharma', city: 'London']],
            LA    : [[name: 'Maradona', city: 'LA']],
            HK    : [[name: 'Zhang', city: 'HK'],
                     [name: 'Ali', city: 'HK'],
                     [name: 'Liu', city: 'HK']],
    ]

### Range ###

使用`..`符号定义的范围是包含性的（即List包含from和to值）。

使用`.. <`符号定义的范围是半开的，它们包括第一个值，但不是最后一个值。

// 全包含的range
    def range = 5..8
    assert range.size() == 4
    assert range.get(2) == 7
    assert range[2] == 7
    assert range instanceof java.util.List
    assert range.contains(5)
    assert range.contains(8)
    
    // 半开的range
    range = 5..<8
    assert range.size() == 3
    assert range.get(2) == 7
    assert range[2] == 7
    assert range instanceof java.util.List
    assert range.contains(5)
    assert !range.contains(8)
    
    //获取range的端点而不使用索引
    range = 1..10
    assert range.from == 1
    assert range.to == 10
    
    // 全包括range
    def range = 'a'..'d'
    assert range.size() == 4
    assert range.get(2) == 'c'
    assert range[2] == 'c'
    assert range instanceof java.util.List
    assert range.contains('a')
    assert range.contains('d')
    assert !range.contains('e')