nj.java

用写的计算角动量的程序。里面含有作者的文章出处。对科技人员非常有用

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.math.*;

/* Nine-J symbol calculator. */

public class NJ extends Applet implements ActionListener, Runnable {
    
    Thread playing;
    
    // declare our A.M values out here
    
    BigRational j1,j2,j3,j4,j5,j6,j7,j8,j9;

    // Let's allow the user to input the numbers as reals. 
    // a double will be just fine here.
    double hj1,hj2,hj3,hj4,hj5,hj6,hj7,hj8,hj9;

    
    // the approximate answer as a 'double'

    double approxanswer;

    
    // panels for the rows of GUI things:
    
    // row one has some text:
    Panel row1 = new Panel();
    Label instructions = new Label
	("Enter the values of a.m. in the boxes below..",Label.CENTER);

    // row two has j1-3
    Panel row2 = new Panel();
    Label j1label = new Label("j1=",Label.RIGHT);
    TextField j1field = new TextField(4);
    Label j2label = new Label("j2=",Label.RIGHT);
    TextField j2field = new TextField(4);
    Label j3label = new Label("j3=",Label.RIGHT);
    TextField j3field = new TextField(4);

    // row three has j4-6
    Panel row3 = new Panel();
    Label j4label = new Label("j4=",Label.RIGHT);
    TextField j4field = new TextField(4);
    Label j5label = new Label("j5=",Label.RIGHT);
    TextField j5field = new TextField(4);
    Label j6label = new Label("j6=",Label.RIGHT);
    TextField j6field = new TextField(4);

    // row four has j7-9
    Panel row4 = new Panel();
    Label j7label = new Label("j7=",Label.RIGHT);
    TextField j7field = new TextField(4);
    Label j8label = new Label("j8=",Label.RIGHT);
    TextField j8field = new TextField(4);
    Label j9label = new Label("j9=",Label.RIGHT);
    TextField j9field = new TextField(4);
    

    // row five has the buttons
    Panel row5 = new Panel();
    Button go = new Button("Go!");
    Button clear = new Button("Clear");

    // row six has the answer
    Panel row6 = new Panel();
    TextField outfield = new TextField(80);

    // row seven has the approximate answer
    Panel row7 = new Panel();
    Label approxlabel = new Label("approx:",Label.RIGHT);
    TextField approxfield = new TextField(40);
    
    
    public void init() {
	
	Font myfont = new Font("SansSerif", Font.PLAIN, 12);
	setFont(myfont);
	
	// set up the layout of the GUI
	
	GridLayout mylayout = new GridLayout(6,1,1,1);
	setLayout(mylayout);
	
	FlowLayout layout1 = new FlowLayout(FlowLayout.CENTER, 1,1);
	row1.setLayout(layout1);
	row1.add(instructions);
	//add(row1);
	
	// do "j" row
	FlowLayout layout2 = new FlowLayout(FlowLayout.CENTER, 1, 1);
	row2.setLayout(layout2);
	row2.add(j1label);
	row2.add(j1field);
	row2.add(j2label);
	row2.add(j2field);
	row2.add(j3label);
	row2.add(j3field);
	add(row2);
	

	FlowLayout layout3 = new FlowLayout(FlowLayout.CENTER, 1, 1);
	row3.setLayout(layout3);
	row3.add(j4label);
	row3.add(j4field);
	row3.add(j5label);
	row3.add(j5field);
	row3.add(j6label);
	row3.add(j6field);
	add(row3);

	FlowLayout layout4 = new FlowLayout(FlowLayout.CENTER, 1, 1);
	row4.setLayout(layout4);
	row4.add(j7label);
	row4.add(j7field);
	row4.add(j8label);
	row4.add(j8field);
	row4.add(j9label);
	row4.add(j9field);
	add(row4);

	FlowLayout layout5 = new FlowLayout(FlowLayout.CENTER, 1, 1);
	row5.setLayout(layout5);
	row5.add(go);
	row5.add(clear);
	add(row5);

	FlowLayout layout6 = new FlowLayout(FlowLayout.CENTER, 1, 1);
	row6.setLayout(layout6);
	outfield.setEditable(false);
	row6.add(outfield);
	add(row6);
	
	FlowLayout layout7 = new FlowLayout(FlowLayout.CENTER, 1, 1);
	row7.setLayout(layout7);
	approxfield.setEditable(false);
	row7.add(approxlabel);
	row7.add(approxfield);
	add(row7);
	// done setting up the layout. Now add some listeners (to the buttons)

	go.addActionListener(this);
	clear.addActionListener(this);
    }
    
    
    public void actionPerformed(ActionEvent event) {
	String command = event.getActionCommand();
	if(command == "Go!") { 
	    playing = new Thread(this);
	    playing.start();
	    go.setEnabled(false);
	    clear.setEnabled(false);
	    outfield.setText("");
	}
	if(command == "Clear") 
	    clearAllFields();
    }
    
    void clearAllFields(){
	j1field.setText(null);
	j2field.setText(null);
	j3field.setText(null);
	j4field.setText(null);
	j5field.setText(null);
	j6field.setText(null);
	j7field.setText(null);
	j8field.setText(null);
	j9field.setText(null);
	outfield.setText(null);
	approxfield.setText(null);
    }
    
    public void run() {
	// This is where the thread starts. 
	
	final BigRational ONE_R = new BigRational(1);
	
	
	// We get the input from the input boxes and convert to the 
	// BigInteger type.
	// This can throw an exception if bad input is given, so let's catch
	// it if we can..
	
	try {
	    hj1 = (new java.lang.Double(j1field.getText())).doubleValue();
	    hj2 = (new java.lang.Double(j2field.getText())).doubleValue();
	    hj3 = (new java.lang.Double(j3field.getText())).doubleValue();
	    hj4 = (new java.lang.Double(j4field.getText())).doubleValue();
	    hj5 = (new java.lang.Double(j5field.getText())).doubleValue();
	    hj6 = (new java.lang.Double(j6field.getText())).doubleValue();
	    hj7 = (new java.lang.Double(j7field.getText())).doubleValue();
	    hj8 = (new java.lang.Double(j8field.getText())).doubleValue();
	    hj9 = (new java.lang.Double(j9field.getText())).doubleValue();
	}
	catch (java.lang.NumberFormatException e) {
	    outfield.setText("All input must be numerical");
	    go.setEnabled(true);
	    clear.setEnabled(true);
	    return;
	}

	// convert decimal input to BigRational.
	j1 = new BigRational(new BigInteger(Long.toString(Math.round(2.*hj1))),
			     new BigInteger("2"));
	j2 = new BigRational(new BigInteger(Long.toString(Math.round(2.*hj2))),
			     new BigInteger("2"));
	j3 = new BigRational(new BigInteger(Long.toString(Math.round(2.*hj3))),
			     new BigInteger("2"));
	j4 = new BigRational(new BigInteger(Long.toString(Math.round(2.*hj4))),
			     new BigInteger("2"));
	j5 = new BigRational(new BigInteger(Long.toString(Math.round(2.*hj5))),
			     new BigInteger("2"));
	j6 = new BigRational(new BigInteger(Long.toString(Math.round(2.*hj6))),
			     new BigInteger("2"));
	j7 = new BigRational(new BigInteger(Long.toString(Math.round(2.*hj7))),
			     new BigInteger("2"));
	j8 = new BigRational(new BigInteger(Long.toString(Math.round(2.*hj8))),
			     new BigInteger("2"));
	j9 = new BigRational(new BigInteger(Long.toString(Math.round(2.*hj9))),
			     new BigInteger("2"));


	
	// Conditions: the j's must satisfy some triangle relations..
	
	if(Math.abs(hj1-hj2) > hj3 || Math.abs(hj1+hj2) < hj3) {
	    outfield.setText("0 ( j1, j2 and j3 do not satisfy the triangle"+
			     " relation)");
	    approxfield.setText("0.0");
	    go.setEnabled(true);
	    clear.setEnabled(true);      
	    return;
	}
	if(Math.abs(hj4-hj5) > hj6 || Math.abs(hj4+hj5) < hj6) {
	    outfield.setText("0 ( j4, j5 and j6 do not satisfy the triangle"+
			     " relation)");
	    approxfield.setText("0.0");
	    go.setEnabled(true);
	    clear.setEnabled(true);      
	    return;
	}
	if(Math.abs(hj7-hj8) > hj9 || Math.abs(hj7+hj8) < hj9) {
	    outfield.setText("0 ( j7, j8 and j9 do not satisfy the triangle"+
			     " relation)");
	    approxfield.setText("0.0");
	    go.setEnabled(true);
	    clear.setEnabled(true);      
	    return;
	}
	if(Math.abs(hj1-hj4) > hj7 || Math.abs(hj1+hj4) < hj7) {
	    outfield.setText("0 ( j1, j4 and j7 do not satisfy the triangle"+
			     " relation)");
	    approxfield.setText("0.0");
	    go.setEnabled(true);
	    clear.setEnabled(true);      
	    return;
	}
	if(Math.abs(hj2-hj5) > hj8 || Math.abs(hj2+hj5) < hj8) {
	    outfield.setText("0 ( j2, j5 and j8 do not satisfy the triangle"+
			     " relation)");
	    approxfield.setText("0.0");
	    go.setEnabled(true);
	    clear.setEnabled(true);      
	    return;
	}
	if(Math.abs(hj3-hj6) > hj9 || Math.abs(hj3+hj6) < hj9) {
	    outfield.setText("0 ( j3, j6 and j9 do not satisfy the triangle"+
			     " relation)");
	    approxfield.setText("0.0");
	    go.setEnabled(true);
	    clear.setEnabled(true);      
	    return;
	}

	// and each of the above triads must be able to couple to each other
	// in the sense that there is not a half-unit of angular momentum 
	// left over.
	if( (new Double(hj1+hj2+hj3)).intValue()*2 != 
	    (new Double(2*(hj1+hj2+hj3))).intValue() ) {
	    outfield.setText("0 (j1 and j2 cannot couple to j3)");
	    approxfield.setText("0.0");
	    go.setEnabled(true);
	    clear.setEnabled(true);      
	    return;
	}
	if( (new Double(hj4+hj5+hj6)).intValue()*2 != 
	    (new Double(2*(hj4+hj5+hj6))).intValue() ) {
	    outfield.setText("0 (j4 and j5 cannot couple to j6)");
	    approxfield.setText("0.0");
	    go.setEnabled(true);
	    clear.setEnabled(true);      
	    return;
	}
	if( (new Double(hj7+hj8+hj9)).intValue()*2 != 
	    (new Double(2*(hj7+hj8+hj9))).intValue() ) {
	    outfield.setText("0 (j7 and j8 cannot couple to j9)");
	    approxfield.setText("0.0");
	    go.setEnabled(true);
	    clear.setEnabled(true);      
	    return;
	}
	if( (new Double(hj1+hj4+hj7)).intValue()*2 != 
	    (new Double(2*(hj1+hj4+hj7))).intValue() ) {
	    outfield.setText("0 (j1 and j4 cannot couple to j7)");
	    approxfield.setText("0.0");
	    go.setEnabled(true);
	    clear.setEnabled(true);      
	    return;
	}
	if( (new Double(hj2+hj5+hj8)).intValue()*2 != 
	    (new Double(2*(hj2+hj5+hj8))).intValue() ) {
	    outfield.setText("0 (j2 and j5 cannot couple to j8)");
	    approxfield.setText("0.0");
	    go.setEnabled(true);
	    clear.setEnabled(true);      
	    return;
	}
	if( (new Double(hj3+hj6+hj9)).intValue()*2 != 
	    (new Double(2*(hj3+hj6+hj9))).intValue() ) {
	    outfield.setText("0 (j1 and j2 cannot couple to j3)");
	    approxfield.setText("0.0");