下面是一个示例代码，用于统计Angular中某个类的实例数量，并在页面上显示出来：

1. 首先，创建一个CounterService服务，用于统计实例数量：

import { Injectable } from '@angular/core';

@Injectable({
  providedIn: 'root'
})
export class CounterService {
  private count: number = 0;

  increment() {
    this.count++;
  }

  decrement() {
    this.count--;
  }

  getCount() {
    return this.count;
  }
}

2. 在需要统计实例数量的组件中，注入CounterService服务并使用它：

import { Component } from '@angular/core';
import { CounterService } from './counter.service';

@Component({
  selector: 'app-component',
  template: `
    

      
Component Instance Count: {{ count }}
      Increment
      Decrement
    
  `,
})
export class MyComponent {
  count: number = 0;

  constructor(private counterService: CounterService) {}

  ngOnInit() {
    this.count = this.counterService.getCount();
  }

  increment() {
    this.counterService.increment();
    this.count = this.counterService.getCount();
  }

  decrement() {
    this.counterService.decrement();
    this.count = this.counterService.getCount();
  }
}

3. 在模块中提供CounterService服务：

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import { CounterService } from './counter.service';
import { MyComponent } from './my.component';

@NgModule({
  declarations: [AppComponent, MyComponent],
  imports: [BrowserModule],
  providers: [CounterService],
  bootstrap: [AppComponent]
})
export class AppModule {}

4. 在AppComponent中使用MyComponent组件：

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  template: `
    
Angular Component Instance Count
    
  `,
})
export class AppComponent {}

5. 在主模块中引导AppComponent：

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import { CounterService } from './counter.service';

@NgModule({
  declarations: [AppComponent],
  imports: [BrowserModule],
  providers: [CounterService],
  bootstrap: [AppComponent]
})
export class AppModule {}

通过以上步骤，就可以在页面上显示组件实例的数量，并且可以通过按钮的点击事件来增加或减少实例数量。