集合 - Map

Main Methods

Method Description
Object put(Object key, Object value) insert object
Object remove(Object key) remove object by key
Object get(Object key) get value by key
boolean containsKey(Object key) search by key
Set keySet() return all keys
Set entrySet() return all key-value pairs (Map.Entry)

Example

package com.test.collection;

import java.util.Map;
import java.util.HashMap;

public class MapTest {

    public static void main(String [] args) {
        Map<Integer,String> map = new HashMap<Integer,String>();

        map.put(10, "dog");
        map.put(11, "cat");
        map.put(12, "fish");
        map.put(13, "bird");

        // traversal
        for(Map.Entry<Integer,String> entry:map.entrySet()) {
            System.out.println(entry.getKey() + " => " + entry.getValue());
        }
        // java 8
        // map.forEach((k, v) -> System.out.printf("%s =>%s%n", k, v));
    }
}

10 => dog
11 => cat
12 => fish
13 => bird

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