bodmass.java

java编程的一些Applets例子。值得深入研究一下。

// Applet source code copyright 1996 Richard E. Wendt III, [e-mail]
//
// This applet calculates the "Body Mass Index" according to the algorithm
//  given in US News & World Report, 8 January 1996, p. 60
//
import java.applet.Applet;
import java.util.Observable;
import java.util.Observer;
import java.awt.TextField;
import java.awt.Event;
import java.awt.Label;
import java.awt.Panel;
import java.awt.GridLayout;
import java.awt.CheckboxGroup;
import java.awt.Checkbox;

class UnitCheckbox extends Checkbox{
	Units un;
	public UnitCheckbox(String s, CheckboxGroup g, boolean b, Units u){
		super(s,g,b);
		un=u;
	}
	public boolean action(Event e, Object o){
	  if(((java.awt.Checkbox)(e.target)).getLabel().compareTo("Metric")==0)
			un.setMetric();
		else un.setUS();
		return true;
	}
}
class Units extends Observable{
	private boolean metric=false;
	CheckboxGroup cbg=new CheckboxGroup();
	UnitCheckbox mcb=new UnitCheckbox("Metric",cbg,false,this);
	UnitCheckbox ucb=new UnitCheckbox("US",cbg,true,this);
			// Start out with US units (lbs and inches)
	public void setMetric(){
		metric=true;
		setChanged();
		notifyObservers(this);
		clearChanged();
	}
	public void setUS(){
		metric=false;
		setChanged();
		notifyObservers(this);
		clearChanged();
	}
	public boolean areMetric(){
		return metric;
	}
	public boolean areUS(){
		return !metric;
	}
	public String USToCurrLength(String s){	// assumes s is in US
		String value;
		double dv;
		if(metric){
			dv=(new Double(s)).doubleValue();
			dv*=2.54;	// 2.54 cm/inch
			value=(new Double(dv)).toString();
		}
		else {
			value=new String(s);
		}
		return value;
	}
	public String CurrToUSLength(String s){
		String value;
		double dv;
		if(metric){
			dv=(new Double(s)).doubleValue();
			dv/=2.54;
			value=(new Double(dv)).toString();
		}
		else {
			value=new String(s);
		}
		return value;
	}
	public String USToCurrWeight(String s){
		String value;
		double dv;
		if(metric){
			dv=(new Double(s)).doubleValue();
			dv*=0.4536;
			value=(new Double(dv)).toString();
		}
		else {
			value=new String(s);
		}
		return value;
	}
	public String CurrToUSWeight(String s){
		String value;
		double dv;
		if(metric){
			dv=(new Double(s)).doubleValue();
			dv/=0.4536;
			value=(new Double(dv)).toString();
		}
		else {
			value=new String(s);
		}
		return value;
	}
	public String getUnitsLength(){
		if(metric) return (new String("cm"));
		else return (new String("in"));
	}
	public String getUnitsWeight(){
		if(metric) return (new String("kg"));
		else return (new String("lb"));
	}
}
class DataEntry extends Observable{
	String data="1";
	public void setData(String s){
		data=new String(s);
		setChanged();
		notifyObservers(data);
		clearChanged();
	}
	public String getData(){
		return data;
	}
	public double getDataAsDouble(){
		return (new Double(data)).doubleValue();
	}
}

class DataField extends TextField implements Observer{
	DataEntry de;
	Label label;

	public DataField(String s, int n, DataEntry d){
		super(s,n);
		de=d;
	}
	public boolean action(Event e, Object o){
		String value;
		value=o.toString();
		de.setData(USValueOfCurrent(value));
		this.setText(value);
		return true;
	}
	public void update(Observable o, Object obj){
		String value;
		value=currValueOfUS(de.getData());
		this.setText(value);
	}
	public String currValueOfUS(String s){
		return (new String(s));
	}
	public String USValueOfCurrent(String s){
		return (new String(s));
	}
	public Label getLabel(){
		return label;
	}
	public String getLabelText(){
		return "";
	}

}
class WeightField extends DataField{
	Units un;

	public WeightField(String s, int n, DataEntry d, Units u){
		super(s,n,d);
		un=u;
	}
	public String currValueOfUS(String s){
		return un.USToCurrWeight(s);
	}
	public String USValueOfCurrent(String s){
		return un.CurrToUSWeight(s);
	}
	public String getLabelText(){
		return new String("Weight ("+un.getUnitsWeight().trim()+"):");
	} 
	public Label getLabel(){
		return new Label(getLabelText());
	}
}
class HeightField extends DataField{
	Units un;
	public HeightField(String s, int n, DataEntry d, Units u){
		super(s,n,d);
		un=u;
	}
	public String currValueOfUS(String s){
		return un.USToCurrLength(s);
	}
	public String USValueOfCurrent(String s){
		return un.CurrToUSLength(s);
	}
	public String getLabelText(){
		return new String("Height ("+un.getUnitsLength().trim()+"):");
	}
	public Label getLabel(){
		return new Label(getLabelText());
	}
}
class BMIField extends TextField implements Observer{
	DataEntry weight;
	DataEntry height;
	DataEntry bmi;
	double wt=0.0,ht=0.0,bmit=0.0;
	public BMIField(String s, int n, DataEntry w, DataEntry h,
		DataEntry b){
		super(s,n);
		weight=w;
		height=h;
		bmi=b;
		this.setEditable(false);
	}
	public void update(Observable o, Object obj){
		String value;
		wt=weight.getDataAsDouble();
		ht=height.getDataAsDouble();
		bmit=(0.45*wt)/((0.025*ht)*(0.025*ht));
		value=(new Double(bmit).toString());
		bmi.setData(value);
		this.setText(value);
	}
}

public class BodMass extends Applet implements Observer{
	Units units=new Units();
	Panel row1=new Panel();
	Panel row2=new Panel();
	Panel row3=new Panel();
	DataEntry weight=new DataEntry();
	WeightField weightField=new WeightField("",8,weight,units);
	Label weightLabel=weightField.getLabel();
	DataEntry height=new DataEntry();
	HeightField heightField=new HeightField("",8,height,units);
	Label heightLabel=heightField.getLabel();
	DataEntry bmi=new DataEntry();
	BMIField bmiField=new BMIField("",7,weight,height,bmi);
	Label bmiLabel=new Label("Body Mass Index =");
	
	public void init(){
		setLayout(new GridLayout(0,1));
		row1.add(units.mcb);
		row1.add(units.ucb);
		units.addObserver(this);
		units.addObserver(weightField);
		units.addObserver(heightField);
		row2.add(weightLabel);
		row2.add(weightField);
		row2.add(heightLabel);
		row2.add(heightField);
		weight.addObserver(bmiField);
		height.addObserver(bmiField);
		row3.add(bmiLabel);
		row3.add(bmiField);
		add(row1);
		add(row2);
		add(row3);
		show();
	}
	public void update(Observable o, Object obj){
		weightLabel.setText(weightField.getLabelText());
		heightLabel.setText(heightField.getLabelText());
	}
}