Java/Collections Data Structure/TreeMap
Содержание
- 1 Check if a particular key exists in Java TreeMap
- 2 Check if a particular value exists in Java TreeMap
- 3 Get Head Map from Java TreeMap
- 4 Get lowest and highest key stored in Java TreeMap
- 5 Get Set view of Keys from Java TreeMap
- 6 Get Size of Java TreeMap
- 7 Get Sub Map from Java TreeMap
- 8 Get Synchronized Map from Java TreeMap
- 9 Get Tail Map from Java TreeMap
- 10 Iterate through the values of Java TreeMap
- 11 Read file content and save to a TreeMap
- 12 Remove all values from Java TreeMap
- 13 Remove value from Java TreeMap
- 14 TreeMap<String, Double>
- 15 Use Generic TreeMap to store Integer as key and String as value
Check if a particular key exists in Java TreeMap
<source lang="java">
import java.util.TreeMap; public class Main {
public static void main(String[] args) { TreeMap<String, String> treeMap = new TreeMap<String,String>(); treeMap.put("1", "One"); treeMap.put("2", "Two"); treeMap.put("3", "Three"); System.out.println(treeMap.containsKey("1")); }
}
</source>
Check if a particular value exists in Java TreeMap
<source lang="java">
import java.util.TreeMap; public class Main {
public static void main(String[] args) { TreeMap<String, String> treeMap = new TreeMap<String, String>(); treeMap.put("1", "One"); treeMap.put("2", "Two"); treeMap.put("3", "Three"); System.out.println(treeMap.containsValue("Three")); }
}
</source>
Get Head Map from Java TreeMap
<source lang="java">
import java.util.SortedMap; import java.util.TreeMap; public class Main {
public static void main(String[] args) { TreeMap<String,String> treeMap = new TreeMap<String,String>(); treeMap.put("1", "One"); treeMap.put("3", "Three"); treeMap.put("2", "Two"); treeMap.put("5", "Five"); treeMap.put("4", "Four"); SortedMap sortedMap = treeMap.headMap("3"); System.out.println("Head Map Contains : " + sortedMap); }
}
</source>
Get lowest and highest key stored in Java TreeMap
<source lang="java">
import java.util.TreeMap; public class Main {
public static void main(String[] args) { TreeMap<String, String> treeMap = new TreeMap<String, String>(); treeMap.put("1", "One"); treeMap.put("2", "Two"); treeMap.put("3", "Three"); treeMap.put("4", "Four"); treeMap.put("5", "Five"); System.out.println("Lowest key: " + treeMap.firstKey()); System.out.println("Highest key: " + treeMap.lastKey()); }
}
</source>
Get Set view of Keys from Java TreeMap
<source lang="java">
import java.util.Iterator; import java.util.TreeMap; import java.util.Set; public class Main {
public static void main(String[] args) { TreeMap<String, String> treeMap = new TreeMap<String, String>(); treeMap.put("1", "One"); treeMap.put("3", "Three"); treeMap.put("2", "Two"); Set st = treeMap.keySet(); Iterator itr = st.iterator(); while (itr.hasNext()){ System.out.println(itr.next()); } st.remove("1"); System.out.println(treeMap.containsKey("1")); }
}
</source>
Get Size of Java TreeMap
<source lang="java">
import java.util.TreeMap; public class Main {
public static void main(String[] args) { TreeMap<String, String> treeMap = new TreeMap<String, String>(); System.out.println("Size of TreeMap : " + treeMap.size()); treeMap.put("1", "One"); treeMap.put("2", "Two"); treeMap.put("3", "Three"); System.out.println("Size of TreeMap after addition : " + treeMap.size()); treeMap.remove("2"); System.out.println("Size of TreeMap after removal : " + treeMap.size()); }
}
</source>
Get Sub Map from Java TreeMap
<source lang="java">
import java.util.SortedMap; import java.util.TreeMap; public class Main {
public static void main(String[] args) { TreeMap<String, String> treeMap = new TreeMap<String, String>(); treeMap.put("1", "One"); treeMap.put("2", "Two"); treeMap.put("3", "Three"); treeMap.put("4", "Four"); treeMap.put("5", "Five"); SortedMap sortedMap = treeMap.subMap("2", "5"); System.out.println("SortedMap Contains : " + sortedMap); }
}
</source>
Get Synchronized Map from Java TreeMap
<source lang="java">
import java.util.Collections; import java.util.Map; import java.util.TreeMap; public class Main {
public static void main(String[] args) { TreeMap treeMap = new TreeMap(); Map map = Collections.synchronizedMap(treeMap); }
}
</source>
Get Tail Map from Java TreeMap
<source lang="java">
import java.util.SortedMap; import java.util.TreeMap; public class Main {
public static void main(String[] args) { TreeMap<String, String> treeMap = new TreeMap<String,String>(); treeMap.put("1", "One"); treeMap.put("3", "Three"); treeMap.put("2", "Two"); treeMap.put("5", "Five"); treeMap.put("4", "Four"); SortedMap sortedMap = treeMap.tailMap("2"); System.out.println("Tail Map Contains : " + sortedMap); }
}
</source>
Iterate through the values of Java TreeMap
<source lang="java">
import java.util.Collection; import java.util.Iterator; import java.util.TreeMap; public class Main {
public static void main(String[] args) { TreeMap<String, String> treeMap = new TreeMap<String,String>(); treeMap.put("1", "One"); treeMap.put("2", "Two"); treeMap.put("3", "Three"); Collection c = treeMap.values(); Iterator itr = c.iterator(); while (itr.hasNext()){ System.out.println(itr.next()); } }
}
</source>
Read file content and save to a TreeMap
<source lang="java">
import java.io.File; import java.io.FileWriter; import java.io.IOException; import java.io.PrintWriter; import java.util.ArrayList; import java.util.Collections; import java.util.List; import java.util.Map; import java.util.Scanner; import java.util.TreeMap; public class LogTest {
public static void main(String[] args) throws IOException { String inputfile = args[0]; String outputfile = args[1]; Map<String, Integer> map = new TreeMap<String, Integer>(); Scanner scanner = new Scanner(new File(inputfile)); while (scanner.hasNext()) { String word = scanner.next(); Integer count = map.get(word); count = (count == null ? 1 : count + 1); map.put(word, count); } scanner.close(); List<String> keys = new ArrayList<String>(map.keySet()); Collections.sort( keys ); PrintWriter out = new PrintWriter(new FileWriter(outputfile)); for (String key : keys) out.println(key + " : " + map.get(key)); out.close(); }
}
</source>
Remove all values from Java TreeMap
<source lang="java">
import java.util.TreeMap; public class Main {
public static void main(String[] args) { TreeMap<String,String> treeMap = new TreeMap<String,String>(); treeMap.put("1", "One"); treeMap.put("2", "Two"); treeMap.put("3", "Three"); treeMap.clear(); System.out.println(treeMap.size()); }
}
</source>
Remove value from Java TreeMap
<source lang="java">
import java.util.TreeMap; public class Main {
public static void main(String[] args) { TreeMap<String,String> treeMap = new TreeMap<String,String>(); treeMap.put("1", "One"); treeMap.put("2", "Two"); treeMap.put("3", "Three"); Object obj = treeMap.remove("2"); System.out.println(obj + " Removed from TreeMap"); }
}
</source>
TreeMap<String, Double>
<source lang="java">
import java.util.Map; import java.util.Set; import java.util.TreeMap; class TreeMapDemo {
public static void main(String args[]) { TreeMap<String, Double> tm = new TreeMap<String, Double>(); tm.put("A", new Double(3.34)); tm.put("B", new Double(1.22)); tm.put("C", new Double(1.00)); tm.put("D", new Double(9.22)); tm.put("E", new Double(-1.08)); Set<Map.Entry<String, Double>> set = tm.entrySet(); for (Map.Entry<String, Double> me : set) { System.out.print(me.getKey() + ": "); System.out.println(me.getValue()); } double balance = tm.get("A"); tm.put("B", balance + 1000); System.out.println(tm.get("A")); }
}
</source>
Use Generic TreeMap to store Integer as key and String as value
<source lang="java">
import java.util.Iterator; import java.util.Map; import java.util.Set; import java.util.TreeMap; public class TreeMapExample {
public static void main(String[] args) { Map<Integer, String> map = new TreeMap<Integer, String>(); // Add Items to the TreeMap map.put(new Integer(1), "One"); map.put(new Integer(2), "Two"); map.put(new Integer(3), "Three"); map.put(new Integer(4), "Four"); map.put(new Integer(5), "Five"); map.put(new Integer(6), "Six"); map.put(new Integer(7), "Seven"); map.put(new Integer(8), "Eight"); map.put(new Integer(9), "Nine"); map.put(new Integer(10), "Ten"); // Use iterator to display the keys and associated values System.out.println("Map Values Before: "); Set keys = map.keySet(); for (Iterator i = keys.iterator(); i.hasNext();) { Integer key = (Integer) i.next(); String value = (String) map.get(key); System.out.println(key + " = " + value); } // Remove the entry with key 6 System.out.println("\nRemove element with key 6"); map.remove(new Integer(6)); // Use iterator to display the keys and associated values System.out.println("\nMap Values After: "); keys = map.keySet(); for (Iterator i = keys.iterator(); i.hasNext();) { Integer key = (Integer) i.next(); String value = (String) map.get(key); System.out.println(key + " = " + value); } }
}
</source>