Guava学习笔记:Guava新增集合类型-Bimap

    @Test
    public void BimapTest(){
        BiMap<Integer,String> logfileMap = HashBiMap.create(); 
        logfileMap.put(1,"a.log");
        logfileMap.put(2,"b.log");
        logfileMap.put(3,"c.log"); 
        System.out.println("logfileMap:"+logfileMap); 
        BiMap<String,Integer> filelogMap = logfileMap.inverse();
        System.out.println("filelogMap:"+filelogMap);
    }

Bimap数据的强制唯一性

  在使用BiMap时,会要求Value的唯一性。如果value重复了则会抛出错误:java.lang.IllegalArgumentException,例如:

    @Test
    public void BimapTest(){
        BiMap<Integer,String> logfileMap = HashBiMap.create(); 
        logfileMap.put(1,"a.log");
        logfileMap.put(2,"b.log");
        logfileMap.put(3,"c.log");         
        logfileMap.put(4,"d.log"); 
        logfileMap.put(5,"d.log"); 
    }

  logfileMap.put(5,"d.log") 会抛出java.lang.IllegalArgumentException: value already present: d.log的错误。如果我们确实需要插入重复的value值,那可以选择forcePut方法。但是我们需要注意的是前面的key也会被覆盖了。

    @Test
    public void BimapTest(){
        BiMap<Integer,String> logfileMap = HashBiMap.create(); 
        logfileMap.put(1,"a.log");
        logfileMap.put(2,"b.log");
        logfileMap.put(3,"c.log"); 
        
        logfileMap.put(4,"d.log"); 
        logfileMap.forcePut(5,"d.log"); 
        System.out.println("logfileMap:"+logfileMap); 
    }
    输出:logfileMap:{5=d.log, 3=c.log, 2=b.log, 1=a.log}

理解inverse方法

  inverse方法会返回一个反转的BiMap,但是注意这个反转的map不是新的map对象,它实现了一种视图关联,这样你对于反转后的map的所有操作都会影响原先的map对象。例如:

@Test
    public void BimapTest(){
        BiMap<Integer,String> logfileMap = HashBiMap.create(); 
        logfileMap.put(1,"a.log");
        logfileMap.put(2,"b.log");
        logfileMap.put(3,"c.log"); 
        System.out.println("logfileMap:"+logfileMap); 
        BiMap<String,Integer> filelogMap = logfileMap.inverse();
        System.out.println("filelogMap:"+filelogMap);
        
        logfileMap.put(4,"d.log"); 

        System.out.println("logfileMap:"+logfileMap); 
        System.out.println("filelogMap:"+filelogMap); 
    }

  输出:

logfileMap:{3=c.log, 2=b.log, 1=a.log}
filelogMap:{c.log=3, b.log=2, a.log=1}
logfileMap:{4=d.log, 3=c.log, 2=b.log, 1=a.log}
filelogMap:{d.log=4, c.log=3, b.log=2, a.log=1}

posted on 2023-01-09 21:25  Louis军  阅读(86)  评论(0编辑  收藏  举报

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