1 package rainbow.thread;  2  3 public class PrintABC {
    4      5     private int counta = 0, countb = 0, countc = 0;  6      7     private boolean printa = false, printb = false, printc = false;  8      9     private int printcount = 0; 10     11     public void printa(){
   12         synchronized(this){
   13             while(!(printcount == 0 || (printb && printc))){
   14                 try {
   15                     wait(); 16                 } catch (InterruptedException e) {
   17                     e.printStackTrace(); 18                 } 19             } 20             System.out.println("A"); 21             printa = true; 22             //reset 23             printb = printc = false; 24             counta++; 25             printcount++; 26             try {
   27                 Thread.sleep(1000); 28             } catch (InterruptedException e) {
   29                 e.printStackTrace(); 30             } 31             notifyAll(); 32         } 33     } 34     35     public void printb(){
   36         synchronized(this){
   37             while(!printa || (counta - countb == 0)){
   38                 try {
   39                     wait(); 40                 } catch (InterruptedException e) {
   41                     e.printStackTrace(); 42                 } 43             } 44             System.out.println("B"); 45             printb = true; 46             countb++; 47             printcount++; 48             try {
   49                 Thread.sleep(1000); 50             } catch (InterruptedException e) {
   51                 e.printStackTrace(); 52             } 53             notifyAll(); 54         } 55     } 56     57     public void printc(){
   58         synchronized(this){
   59             while(!printb || (countb - countc == 0)){
   60                 try {
   61                     wait(); 62                 } catch (InterruptedException e) {
   63                     e.printStackTrace(); 64                 } 65             } 66             System.out.println("C"); 67             printc = true; 68             //reset a 69             printa = false; 70             countc++; 71             printcount++; 72             try {
   73                 Thread.sleep(1000); 74             } catch (InterruptedException e) {
   75                 e.printStackTrace(); 76             } 77             notifyAll(); 78         } 79         80     } 81 82     public int getPrintcount() {
   83         return printcount; 84     } 85 86     public void setPrintcount(int printcount) {
   87         this.printcount = printcount; 88     } 89 90 }

1 package rainbow.thread;  2  3 public class PrintThread implements Runnable {
    4  5     private PrintABC abc = null;  6      7     public PrintThread(PrintABC abc){
    8         this.abc = abc;  9     } 10     11     public void run() {
   12         while(abc.getPrintcount() <= 30){
   13             abc.printa(); 14         } 15     } 16 17 }

1 package rainbow.thread;  2  3 public class TestThread {
    4  5     public static void main(String[] args) {
    6         PrintABC abc = new PrintABC();  7          8         new Thread(new PrintThread(abc)).start();  9         new Thread(new PrintThread1(abc)).start(); 10         new Thread(new PrintThread2(abc)).start(); 11     } 12 13 }