76 lines
2.0 KiB
Java
76 lines
2.0 KiB
Java
/*
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* Copyright (C) 2019 The Dagger Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package dagger.example.atm;
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import java.math.BigDecimal;
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import java.util.HashMap;
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import java.util.Map;
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import javax.inject.Inject;
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import javax.inject.Singleton;
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/** A database that stores all of its data in memory. */
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@Singleton
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final class InMemoryDatabase implements Database {
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private final Map<String, Account> accounts = new HashMap<>();
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@Inject
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InMemoryDatabase() {}
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@Override
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public Account getAccount(String username) {
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return accounts.computeIfAbsent(username, InMemoryAccount::new);
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}
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private static final class InMemoryAccount implements Account {
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private final String username;
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private BigDecimal balance = BigDecimal.ZERO;
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InMemoryAccount(String username) {
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this.username = username;
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}
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@Override
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public String username() {
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return username;
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}
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@Override
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public void deposit(BigDecimal amount) {
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checkNonNegative(amount, "deposit");
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balance = balance.add(amount);
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}
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@Override
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public void withdraw(BigDecimal amount) {
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checkNonNegative(amount, "withdraw");
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balance = balance.subtract(amount);
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}
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private void checkNonNegative(BigDecimal amount, String action) {
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if (amount.signum() == -1) {
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throw new IllegalArgumentException(
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String.format("Cannot %s negative amounts: %s", action, amount));
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}
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}
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@Override
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public BigDecimal balance() {
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return balance;
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}
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}
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}
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