Map 接口

Map方法举例

import java.util.*;
public class TestMap2 {
  public static void main(String args[]) {
    Map<String, Integer> m1 = new HashMap<String , Integer>();
    m1.put("one", 1);
    m1.put("two", 2);
    m1.put("three", 3);

    System.out.println(m1.size());
    System.out.println(m1.containsKey("one"));

    if(m1.containsKey("two")) {
      //int i = ((Integer)m1.get("two")).intValue();
      int i = m1.get("two");
      System.out.println(i);
    }

  }
}

TestMap2.java

import java.util.*;
public class TestArgsWords {
  //private static final Integer ONE = new Integer(1);
  private static final int ONE = 1;
  public static void main(String args[]) {
    Map m = new HashMap();
    for (int i = 0; i < args.length; i++) {
      //Integer freq = (Integer) m.get(args[i]);

      int freq = (Integer) m.get(args[i]) == null ? 0 : (Integer) m.get(args[i]);
      //m.put(args[i],(freq == null? ONE : new Integer(freq.intValue() + 1)));
      m.put(args[i], freq==0 ? ONE : freq + 1);
    }
    System.out.println
        (m.size() + " distinct words detected:");
    System.out.println(m);
  }
}

TestArgsWords

JDK1.5泛型

import java.util.*;

public class BasicGeneric {
    public static void main(String[] args) {
        List<String> c = new ArrayList<String>();
        c.add("aaa");
        c.add("bbb");
        c.add("ccc");
        for(int i=0; i<c.size(); i++) {
            String s = c.get(i);
            System.out.println(s);
        }

        Collection<String> c2 = new HashSet<String>();
        c2.add("aaa"); c2.add("bbb"); c2.add("ccc");
        for(Iterator<String> it = c2.iterator(); it.hasNext(); ) {
            String s = it.next();
            System.out.println(s);
        }
    }
}

class MyName implements Comparable<MyName> {
    int age;

    public int compareTo(MyName mn) {
        if(this.age > mn.age) return 1;
        else if(this.age < mn.age) return -1;
        else return 0;
    }
}

BasicGeneric.java

import java.util.*;
public class TestArgsWords2 {
  private static final int ONE = 1;
  public static void main(String args[]) {
    Map<String, Integer> m = new HashMap<String, Integer>();
    for (int i = 0; i < args.length; i++) {

      if(!m.containsKey(args[i])) {
          m.put(args[i], ONE);
      }
      else {
          int freq = m.get(args[i]);
          m.put(args[i], freq + 1);
      }

    }
    System.out.println
        (m.size() + " distinct words detected:");
    System.out.println(m);
  }
}

TestArgsWords2.java

总结