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>
